Got a virus cant install anti-virus, malware, lost recovery disk

Computer: Emachine
Model Number: EL1200
OS: Windows Xp
Problem: The screen kept going completely black, then it would pop up comand prompt, close it. Open it close it, and so on. Until it froze the whole system. I found out my mom has no anti-virus...

on it. I tried to install Malware, and Avast aslo Avg using a flashdisk cause the computer will no longer go online. I couldnt get Avast, or Avg. Malware would instal but close after 2seconds of scanning then it wouldnt open again. I tried it about 10 times. Safe mode wont work. Most applications automaticly close. Sometimes itll boot up okay, sometimes itll be a blue screen with my arrow. Sometime itll boot up to a blue screen my arrow, and the start bar.

Edit: I Tried the Avira Boot sector Repair. Now itll go to the log in.. when I try to log in it logs off right away.. Safe mode still wont work..

you have done everything I know how to do except discharge a firearm in its general direction

im very, very pc savvy and that makes no sence 2 me :S

if you can, back up all your images and files on cd/dvd and reinstall windows

emachines give you a reinsatll disk so no probs

as soon as you back up::: download firefox, disable access to internet explorer and download AVG9: the paid for version is better

from the EL1200 page on emachines.com

Telephone Technical Support
Customer Care representatives are available 5 am to 12 midnight (PST) seven days a week.

United States866-586-2237*
Canada866-598-2237*
*Long distance charges may apply, depending on your calling area.

I dont think this emachine gave me a reinstall disk for windows.. I was using firefox when it happened... And I definitly plan on getting an anti-virus.. haha..