I'd say it sounds more like you've got a massive spyware infestation, possibly even a virus or worm. It also sounds like the damage has progressed to a point where the best option would be to format and start over.
Back up anything you don't want to lose, and then stick in the recovery disc that came with the system. Let it do it's thing, then you can start putting those files back.
This time make sure you have a virus scanner and that it's constantly updated, and download a couple of spyware removal tools and update/run all of them freequently (at least once a week).
having problems with my system. Many programs fail to operate and some games dissappear all by them selves. One problem is when I try to create a picture memmories disc using Hewlett Packers memmories disc creator I keep getting a message which states corrupt file or video. System boots up very slowly. mouse pointer flashes on some games. Is it possible that a file may be missing from xp and if so how do I uninstall xp and then reinstall. Help