I like to start off by deleting as many of the temp files as possible:
1 – From “My Computer” or “Explorer” click on Tools, select Folder Options
2 – Then from the Tabs at the top, select View
3 – Now click on the Show hidden files and make sure that hide system files is not checked
Close all these screens
Reboot into Safe Mode (while rebooting hit F8 before the windows screen appears)
4 – Click on Start then Search
5 – On the left panel select All Files and Folders
6 – For search criteria, put in the following for our first search: ~*.* and then click on Search
7 – When it is through searching, you want to hold down the shift key and select A to highlight all the files that were found in the search
8 – Now, hit the Delete Key
9 – Click on the Back to do another search
10 – Now this time for search criteria use: *.tmp and then click on Search
11 – Repeat the same steps above for highlighting and deleting these files
12 – Now, we want to browse to c:\windows\temp folder
13 – Highlight all the files and delete them

Now do a Check Disk:

Click on Start, Programs, Accessories, System Tools, Check Disk
It will give you a message stating that it will perform this action during the next startup, so reboot now.

Now do a Disk Defrag:
Click on Start, Programs, Accessories, System Tools, Defrag Disk
Now check your Anti-Virus Program to make sure that:
1 – Your definitions are up-to-date (update if necessary)
2 – It is scheduled to perform disk scanning on a regular basis (if not, config it to do a regular scan)
If your computer hasn’t been scanned in at least the last week, go ahead and start one now
Now check any and all of your spyware detector programs just like you did for the anti-virus program
Now check your firewall programs just like you did for the anti-virus program
Finally, go to Windows Updates and make sure that all the updates have been successfully completed!