Proxus,
Lets start with a Virus Scan:
Tend Micro's Housecall
If you have a network connection, it might be worth installing your OS again. You can transfer your Data to another comp on your network.
With Win2k and WinXP you can do an install of your OS and only lose the files in your Windows Directory. All your Data would be untouched. It is not a bad idea to do a fresh install of your OS since your current install is over a year old.
Take Care,
Richard