If SFC /SCANNOW didn't fix this problem then try these steps::
Remove unused programs
Install and run antispyware software
Free up wasted space with Disk Cleanup tool
Defragment your hard disk drive
Disconnect unused network connections:
Click Start, and then click My Computer.
On the Tools menu, click Disconnect Network Drive.
Select the network drives that you no longer need, and then click OK.
Click Start - Run, type in %temp% and then click OK.
Once that temp folder is open and you can view its contents, select and delete EVERYTHING that's inside it.
It's all junk and is a good place for "nasties" to hide.
If a few files resist being deleted, that's normal. Leave them alone and delete EVERYTHING else.
Repeat the steps with c:\windows\temp
After you're done with both temp folders, restart the computer.