Computer will not start, black screen

My computer got a virus, now when i turn it on, the screen turns black where the log in screen should occur. I can not enter safemode either, or any other of the options listed when i select F8, Everything just leads to the black screen. Please help me! What can i do? I dont have the option of downloading an antivirus software, because I cant even get into my computer since it doesnt start up. System repair, restore, safe mode, all arnt options because when i select them, it just leads to the black screen again.

I am asking this from another computer.

the computer im having trouble with is a dell windows xp desktop.