My computer restarting unexpectedly when I'm trying to scan for viruses... My IE and WMP is not working now. I tried to do online virus scan but most of online virus scanner only accepts IE. I installed Netscape and tried to use Trend Micro Housecall. I downloaded the program to use it and my computer restarting unexpectedly again. Everytime I tried to scan for virus or playing online games, my computer will restarting unexpectedly. My computer works fine surfing online, download music or games, but it prevents me to use virus scanner. I tried to back up my files but I afraid my computer will restart again when I'm burning my important files. Please help me.

I'm using Windows XP. Pentium 1.5GHZ, 128 mb ram, geforce 2 mx video card.