I have a trojan virus and am unable to completely wipe my computer and start over?

I have a refurbished Dell Optiplex GX270 that came with XP service pack 2. I've tried reinstalling, but my old files (and corrupted system32 files) are still there. I tried completely wiping via fdisk, but it won't let me. I even tried a fresh installation, overwriting all the other files but all the old files are still there and I'm still having problems (won't let me install office, won't let me launch firefox, just to name a few.)

I ran a avg anti-virus but it tells me it can't heal the files it's warning me about.

Anyone have any suggestions?

Thanks, Finger...that really helped I think. I hope.

I don't see how it could prevent you from completely wiping the hard drive. If you go into your BIOS and set the primary boot to your CD drive then boot up with your XP SP2 disc in, and choose to install XP, it should ask you which partition you want it in. Theoretically you should be able to just click on the partition and delete it, then reinstall your OS.

I can't see it surviving that, nor preventing it.

USE AVAST ANTIVIRUS, AVG SUCKS BIG THINGS. BUT HERE'S A HINT ANYTHING YOU DOWNLOAD IT USE AVAST TO SCAN IT FOR VIRUSES BEFORE YOU OPEN IT UP!

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