Registry error while trying to install Oracle 11g on Win 2008 R2
From this link:

An old ORACLE_HOME had not been deinstalled/removed correctly and the following registry information still existed:

[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\OracleMTSRecoveryService]

[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\OracleMTSRecoveryService\Protid_0]  
"Name"="HTTP"  
"Host"="hostname"  
"Port"="49155"

[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\OracleMTSRecoveryService\Setup]  
"NumberOfInstalls"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\OracleMTSRecoveryService\Setup\All Versions]

[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\OracleMTSRecoveryService\Setup\All Versions\1]  
"Version"="11.2.0.1.0"  
"Home"="SOFTWARE\\ORACLE\\KEY_OraDb11g_home2"

[HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\OracleMTSRecoveryService\Setup\Current Version]  
"Version"="11.2.0.1.0"  
"Home"="SOFTWARE\\ORACLE\\KEY_OraDb11g_home2"


Please do the following,


Verify that:
the above registry keys exist in the Windows registry, and
they point to an old %ORACLE_HOME% which no longer exists on the server
If the registry keys do not exist or if they point to a valid %ORACLE_HOME% on the server, there is another cause for the error which needs to be investigated further. Do not perform step 2.
After verifying both of the above points, remove the above registry keys and perform the 11.2 installation again. The error should no longer occur.