[EDIT: Check the link above, it looks good.]
There seems to be some ucking background task that keeps popping up every few seconds. Its a shame that M$ hasnt sorted out that kind of mess - these programs should come up in the background - if the user wanted these to come up in front, he would have clicked them in the first place. AARGH!
Sorry for the anti-M$ rant.
Scan your PC for viruses and other malware. Some of these programs are quite malicious - they take screenshots of your browser and send them to hackers.
If you cannot find any, it is probably time to reinstall the OS. Make copies of all data you need, reformat the partition (and limiting the OS partition to a sensible size would be good, too), and reinstall from DVD/CD. Then, set up your drivers and firewall/antivirus and restor the data, scanning them as they come in.
Yeah, reinstall is a b***h. :( Hope you find the malware.