The problem you have now may not necessarily be the same as the one you had before - you killed the original virus.
Last week my laptop (XP) was behaving exactly as your machine. A shutdown could take several minutes.
I used Task Manager and found a process was taking up 98% of the CPU cycles even when I had no applications running. I downloaded a free utility called Process Explorer and installed it - it just confirmed what was happening but in a much prettier way.
Searches (very slow searches) on the web suggested this that and the other and I tried all the suggested fixes for an hour or two with no success.
I did a system restore and immediately all was well - the process previously consuming all the CPU is now using under 2%.
Things you might try for free are Spybot Search & Destroy and clearing out everything in the start up list - there are articles on the web that will explain how to do it - quick and easy.
Try to find out using task manager or even Process Explorer what's happening inside the machine CPU / Network / Applications / Processes - any Virus worth it's salt will not give the game away by making the machine run slowly so my guess is that your current problem is not virus related.
Good luck...
Peccavi
January 2010
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