Problem:
I got a connection problem with SSRS, SSAS, or SSIS earlir today with my old PC - Win7(32-bit) and SQL Server 2008. Finally I figured out it is because the PC was connecting to a wrong server name. I had changed the PC name months ago. So the next logic question is that can I remove the outdated server names from the dropdown list in SSMS? Yes.
Solution:
1. Go to C:\Users\[user]\AppData\Roaming\Microsoft\Microsoft SQL Server\100\Tools\Shell\
2. Then delete the SqlStudio.bin file.
Update on 2/23/2014:
The removal of the unused old instance name has been easier since SQL Server Denali CTP 3. Simply highlight it, press on the delete key.
More info on http://blogs.msdn.com/b/managingsql/archive/2011/07/13/deleting-old-server-names-from-quot-connect-to-server-quot-dialog-in-ssms.aspx
