Unable to re-install an instance using the original instance name We are trying to uninstall and re-install a 2008R2 instance.  We have uninstalled the database engine but when we tried to re-install it we got the error "Original instance id\name in use".  

The instance is on a VM machine (no cluster).  Unfortunately there is another (production) instance on the same machine.  

The steps taken were as follows:


Back up the databases
Uninstall the instance
Reboot
Attempt re-install failed
Review registry for any possible references to the database engine and that instance name and remove them.
Attempt re-install - same error.


We did discover that there is a reporting server instance with the old instance name already installed but I wouldn't have thought that the instance name on a reporting server instance would affect the install of a database engine instance.

Any suggestions on what we are missing?
The cleanest solution IMHO will be to remove reporting services, too, as part of cleaning the old instance off the machine. Until you've cleaned off everything service-related, that instance name still "exists" - and it can be a really thorny and frustrating experience trying to remove all the registry entries, GUID by agonizing GUID.

I suspect that SQL Server must keep some things around e.g. for connectivity to SSRS from external sources via the instance name. This is why you can't just pave a new instance over top of it.

The other alternative would be to leave your SSRS instance intact, but install the new instance with a different name, and just update application connection strings, aliases, DNS etc. so that they will connect to the new instance name (hopefully this change will be as transparent as possible).