Just had the same problem with a customers netbook. Go into Safe Mode with Command Prompt, have MBam latest ready on a memory stick. Install via command window ie. something like E:/mbamsetup.exe It won't update (at least it wouldn't for me) but I ran on quick scan and came up with 9 viruses, a couple of trojans, backdoor.bot and pups. Removed and restarted Windows XP in this case and it's fixed. Got a bit more work to do on netbook but that's the starting point for you. Gonna update and run full scan now I can get back online. Hope this helps!