Cheap. With the release of this year's line of GFX, you'd be best off buying a 9800 Pro. They are CHEAP compared to $800 or $900 last year.
I would definetly format, and then use norton ghost to make a restore disk so that u never get this problem again. EVER!
reformatting would solve all your problems^^ but the real challenge would be to hunt the trojan down and kill it.
