Hey, /r/techsupport, i could really use some help

The problem: Last year, I got a new laptop and gave my old Windows XP (service pack 3) desktop to my mother and stepdad. Now it has 8 viruses, 6 of which are trojans, 2 of which are unnamed, 3 of which are still infecting the computer and Norton can't quarantine them. The system is telling me hy hard drive and RAM have failed, but I can get it to boot up to the desktop (but no wallpaper). The start menu is empty and when I go to my user, the entire folder is empty, but when I access it from command prompt (from safe mode) I can see most of my documents.

The fun part: My WINDOWS system folder is missing, ergo no access to anything in it. My Cd drive is broken so that's out of the question.

The question: What can I do? All my files are off the computer so I could care less what I do to the hard drive or the system itself. I just really hope there's something I can do because this was my first computer I helped build, I don't want to lose it. And no, my mom can't afford another computer (not that Im sure I want to trust her with one anymore).

Any help would be greatly appreciated.