This is related to your soundmix.exe virus issue, right?
I had this a month ago - stupid cousin of mine connected his CF card to my computer; I had real-time AV scanner temporarily disabled...shit happened. The thing deletes all the permissions for the registry and all kinds of funny stuff happens - for one, you can't launch any applications.
1. Go to your registry editor (Run->Type 'regedit')
2. Right-click each predefined registry folder (HKEY_LOCAL_MACHINE etc.) and select 'Permissions'
3. Click on Advanced in the Security tab, regain Ownership of the folder and assign Administrators/Users/System rights to the registry.
4. Repeat for the rest of the folder.
The thing is, something would keep messing up on my computer. Ultimately, I gave up trying to fix everything and just did a reinstall. I hated that damn virus. :| The one time I disabled my scanner and someone hooks up their stupid infected memory card in my absence.