The registry keys that Xiao-Min mentioned are the information for a installed SQL Server service or installer information. If your sql Server instance is removed, they are not needed any more. But before you perform any registry modifications,
I recommend that you first fully backup your registry.
If this issue persists, please help collect the following information:
1. SQL Server Setup logs
By default, it is at C:\Program Files\Microsoft SQL Server\100\Setup Bootstrap\Log.
2. Windows event logs
Open Windows Event Viewer, save the event logs for Application, Security, Setup and System to files.
3. Process Monitor Trace
Download the tool here,
http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx. Then recover your registry. Run Process Monitor on your computer, perform actions to reproduce your issue, stop the trace and save the trace to a file.
You can compress these files to a .zip file, but anyway the size of these files may be still large. To help you upload the information to Microsoft, could you please send me (sqltnsp_at_microsoft_dot_com) an email with the subject "<To
Charles><the url of this thread>" first? Then I will let you know how to upload the large files to us via email.