After you have updated, boot into safe mode (F8) and run it then.

That is an old version of McAfee (I use 7.0) so I am guessing. If you delete a file you just mark the space as available, you do not get rid if the data........it could be that?

Also:

1. defrag your system
2. empty the deleted items folder in Outlook
3. Compress the folders in Outlook

And as you are using XP, watch out for system restore...........you can restore malware as well as your system. There are instructions on the McAfee site on how to disable restore whilst you do a proper cleanup.

Good luck