Registered Server window does not show Database Engine or Local Server Groups
In the folder %APPDATA%\Microsoft\Microsoft SQL Server\110\Tools\Shell you should find a file named RegSrvr.xml. That's the file where Management Studio stores local registered servers. If the file is missing or corrupt, SSMS won't display anything.

In this case, you can create a new file and paste this:

&lt;?xml version="1.0"?&gt;
&lt;model xmlns="http://schemas.serviceml.org/smlif/2007/02"&gt;
  &lt;identity&gt;
    &lt;name&gt;urn:uuid:96fe1236-abf6-4a57-b54d-e9baab394fd1&lt;/name&gt;
    &lt;baseURI&gt;http://documentcollection/&lt;/baseURI&gt;
  &lt;/identity&gt;
  &lt;xs:bufferSchema xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
    &lt;definitions xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08"&gt;
      &lt;document&gt;
        &lt;docinfo&gt;
          &lt;aliases&gt;
            &lt;alias&gt;/system/schema/RegisteredServers&lt;/alias&gt;
          &lt;/aliases&gt;
          &lt;sfc:version DomainVersion="1" /&gt;
        &lt;/docinfo&gt;
        &lt;data&gt;
          &lt;xs:schema targetNamespace="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified"&gt;
            &lt;xs:element name="RegisteredServersStore"&gt;
              &lt;xs:complexType&gt;
                &lt;xs:sequence&gt;
                  &lt;xs:any namespace="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" processContents="skip" minOccurs="0" maxOccurs="unbounded" /&gt;
                &lt;/xs:sequence&gt;
              &lt;/xs:complexType&gt;
            &lt;/xs:element&gt;
            &lt;xs:element name="ServerGroup"&gt;
              &lt;xs:complexType&gt;
                &lt;xs:sequence&gt;
                  &lt;xs:any namespace="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" processContents="skip" minOccurs="0" maxOccurs="unbounded" /&gt;
                &lt;/xs:sequence&gt;
              &lt;/xs:complexType&gt;
            &lt;/xs:element&gt;
            &lt;RegisteredServers:bufferData xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08"&gt;
              &lt;instances xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08"&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:RegisteredServersStore xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:ServerGroups&gt;
                        &lt;sfc:Collection&gt;
                          &lt;sfc:Reference sml:ref="true"&gt;
                            &lt;sml:Uri&gt;/RegisteredServersStore/ServerGroup/AnalysisServicesServerGroup&lt;/sml:Uri&gt;
                          &lt;/sfc:Reference&gt;
                          &lt;sfc:Reference sml:ref="true"&gt;
                            &lt;sml:Uri&gt;/RegisteredServersStore/ServerGroup/CentralManagementServerGroup&lt;/sml:Uri&gt;
                          &lt;/sfc:Reference&gt;
                          &lt;sfc:Reference sml:ref="true"&gt;
                            &lt;sml:Uri&gt;/RegisteredServersStore/ServerGroup/DatabaseEngineServerGroup&lt;/sml:Uri&gt;
                          &lt;/sfc:Reference&gt;
                          &lt;sfc:Reference sml:ref="true"&gt;
                            &lt;sml:Uri&gt;/RegisteredServersStore/ServerGroup/IntegrationServicesServerGroup&lt;/sml:Uri&gt;
                          &lt;/sfc:Reference&gt;
                          &lt;sfc:Reference sml:ref="true"&gt;
                            &lt;sml:Uri&gt;/RegisteredServersStore/ServerGroup/ReportingServicesServerGroup&lt;/sml:Uri&gt;
                          &lt;/sfc:Reference&gt;
                          &lt;sfc:Reference sml:ref="true"&gt;
                            &lt;sml:Uri&gt;/RegisteredServersStore/ServerGroup/SqlServerCompactEditionServerGroup&lt;/sml:Uri&gt;
                          &lt;/sfc:Reference&gt;
                        &lt;/sfc:Collection&gt;
                      &lt;/RegisteredServers:ServerGroups&gt;
                    &lt;/RegisteredServers:RegisteredServersStore&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore/ServerGroup/AnalysisServicesServerGroup&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:ServerGroup xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:Parent&gt;
                        &lt;sfc:Reference sml:ref="true"&gt;
                          &lt;sml:Uri&gt;/RegisteredServersStore&lt;/sml:Uri&gt;
                        &lt;/sfc:Reference&gt;
                      &lt;/RegisteredServers:Parent&gt;
                      &lt;RegisteredServers:Name type="string"&gt;AnalysisServicesServerGroup&lt;/RegisteredServers:Name&gt;
                      &lt;RegisteredServers:ServerType type="ServerType"&gt;AnalysisServices&lt;/RegisteredServers:ServerType&gt;
                    &lt;/RegisteredServers:ServerGroup&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore/ServerGroup/CentralManagementServerGroup&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:ServerGroup xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:Parent&gt;
                        &lt;sfc:Reference sml:ref="true"&gt;
                          &lt;sml:Uri&gt;/RegisteredServersStore&lt;/sml:Uri&gt;
                        &lt;/sfc:Reference&gt;
                      &lt;/RegisteredServers:Parent&gt;
                      &lt;RegisteredServers:Name type="string"&gt;CentralManagementServerGroup&lt;/RegisteredServers:Name&gt;
                      &lt;RegisteredServers:ServerType type="ServerType"&gt;DatabaseEngine&lt;/RegisteredServers:ServerType&gt;
                    &lt;/RegisteredServers:ServerGroup&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore/ServerGroup/DatabaseEngineServerGroup&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:ServerGroup xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:Parent&gt;
                        &lt;sfc:Reference sml:ref="true"&gt;
                          &lt;sml:Uri&gt;/RegisteredServersStore&lt;/sml:Uri&gt;
                        &lt;/sfc:Reference&gt;
                      &lt;/RegisteredServers:Parent&gt;
                      &lt;RegisteredServers:Name type="string"&gt;DatabaseEngineServerGroup&lt;/RegisteredServers:Name&gt;
                      &lt;RegisteredServers:ServerType type="ServerType"&gt;DatabaseEngine&lt;/RegisteredServers:ServerType&gt;
                    &lt;/RegisteredServers:ServerGroup&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore/ServerGroup/IntegrationServicesServerGroup&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:ServerGroup xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:Parent&gt;
                        &lt;sfc:Reference sml:ref="true"&gt;
                          &lt;sml:Uri&gt;/RegisteredServersStore&lt;/sml:Uri&gt;
                        &lt;/sfc:Reference&gt;
                      &lt;/RegisteredServers:Parent&gt;
                      &lt;RegisteredServers:Name type="string"&gt;IntegrationServicesServerGroup&lt;/RegisteredServers:Name&gt;
                      &lt;RegisteredServers:ServerType type="ServerType"&gt;IntegrationServices&lt;/RegisteredServers:ServerType&gt;
                    &lt;/RegisteredServers:ServerGroup&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore/ServerGroup/ReportingServicesServerGroup&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:ServerGroup xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:Parent&gt;
                        &lt;sfc:Reference sml:ref="true"&gt;
                          &lt;sml:Uri&gt;/RegisteredServersStore&lt;/sml:Uri&gt;
                        &lt;/sfc:Reference&gt;
                      &lt;/RegisteredServers:Parent&gt;
                      &lt;RegisteredServers:Name type="string"&gt;ReportingServicesServerGroup&lt;/RegisteredServers:Name&gt;
                      &lt;RegisteredServers:ServerType type="ServerType"&gt;ReportingServices&lt;/RegisteredServers:ServerType&gt;
                    &lt;/RegisteredServers:ServerGroup&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
                &lt;document&gt;
                  &lt;docinfo&gt;
                    &lt;aliases&gt;
                      &lt;alias&gt;/RegisteredServersStore/ServerGroup/SqlServerCompactEditionServerGroup&lt;/alias&gt;
                    &lt;/aliases&gt;
                    &lt;sfc:version DomainVersion="1" /&gt;
                  &lt;/docinfo&gt;
                  &lt;data&gt;
                    &lt;RegisteredServers:ServerGroup xmlns:RegisteredServers="http://schemas.microsoft.com/sqlserver/RegisteredServers/2007/08" xmlns:sfc="http://schemas.microsoft.com/sqlserver/sfc/serialization/2007/08" xmlns:sml="http://schemas.serviceml.org/sml/2007/02" xmlns:xs="http://www.w3.org/2001/XMLSchema"&gt;
                      &lt;RegisteredServers:Parent&gt;
                        &lt;sfc:Reference sml:ref="true"&gt;
                          &lt;sml:Uri&gt;/RegisteredServersStore&lt;/sml:Uri&gt;
                        &lt;/sfc:Reference&gt;
                      &lt;/RegisteredServers:Parent&gt;
                      &lt;RegisteredServers:Name type="string"&gt;SqlServerCompactEditionServerGroup&lt;/RegisteredServers:Name&gt;
                      &lt;RegisteredServers:ServerType type="ServerType"&gt;SqlServerCompactEdition&lt;/RegisteredServers:ServerType&gt;
                    &lt;/RegisteredServers:ServerGroup&gt;
                  &lt;/data&gt;
                &lt;/document&gt;
              &lt;/instances&gt;
            &lt;/RegisteredServers:bufferData&gt;
          &lt;/xs:schema&gt;
        &lt;/data&gt;
      &lt;/document&gt;
    &lt;/definitions&gt;
  &lt;/xs:bufferSchema&gt;
&lt;/model&gt;


This is what an empty registered servers file looks like in SSMS 2012. It should bring your SSMS back to normal.