Computer help forum: Computer freeze-up During Download

First the specifics on my computer:

Model: Gateway 500SE
Intel Pentium 4, 1600 MHz, 100MHz external bus
Memory: 768MB physical
Windows XP SP1 (Windows XP 5.1.2600 Service Pack 1)
Intel Intel PRO/100 VE Network Connection, Cable Modem

My computer will often freeze-up during a high-speed download, or when I'm downloading a few things at once. If I'm able to bring up the task manager (which I'm not able to do), I've noticed that it'll say CPU usage is at 100% when the problem occurs. More often than not, the computer freezes up before I'm able to bring up task manager.

For instance, It's happened if I'm using a bittorrent program to download large-sized files (television episodes) and when I've tried to download trial versions of software programs.

Some related things I've noticed:

--Task manager will not work, and I have to either unplug the computer or turn off the computer without shutting it down. I've waited half an hour sometimes to see if it'll unfreeze, all to no avail.

--I've been able to bring up My Computer, and cannot open "view system information" but can open other options in My Computer. Don't know if that's worth mentioning, just thought I would because I noticed it.

--Just before the computer freezes up, the internet connection will die completely.

--I've run a few different virus checking programs (Norton and Housecall), and they have come up with nothing. Also using ZoneAlarm Firewall program.

This has been happening for 2 weeks, and cannot figure out what is causing the issue. Any ideas?