MB, RAM, and CPU are probably fine. Easiest fix: buy new HD for <$50, fresh install of whatever OS you have, patch it, put some sort of anti-virus on it, reinstall whatever progs you need. Buy an external HD enclosure for <$20, put the old drive in it. You can grab your pictures/pr0n/music off of it. ***edit: when you're sure you have everything you want off of the old drive, format it, then use it as a backup of \my documents, or wherever you store your "stuff". If/when your machine again starts acting strangely, all your goodies are backed up, so just wipe it and reinstall. ***edit #2: Once you get the machine back to where you want it (patched, a-v, progs installed) but BEFORE you put all your "stuff" on it, set a system restore point. If/when it all goes to hell again, revert to the restore point. If you're feeling adventuresome, download Ubuntu (or some other Linux), burn it to CD, boot from the CD, and try it as your OS for a day or evening. If you think "yeah, I could use this", then install it to the HD. I've been using it (Linux) as my main OS for around 10 years - feel free to ask/PM for help.