Internet slow on one PC and not the other?

Hello, I've been chasing this problem for about 2 months now. My computer and my wife's computer are hooked up to the same router/firewall. Hers is on a 8011b wireless card and mines on a 3com 100mbit nic. However for the last two months the internet via downloads and just normal surfing is slow on mine. According to speakeasy hers is like 4000kbps down and mine is 780kbps. My machine is running Windows XP, and hers is windows 2000. I've tried different cat5 cables, 2 new nics, 1 wireless nic (same model as the one she has). I've done every search/scan for viruses/malware/spyware I can find and still nothing has even found anything let alone fix anything. I've updated .net framework and up to service pack 2 for windows xp. I ran WinsocXPfix and every other tweak I can find. Though nothing seems to change anything. I'm just short of formatting the harddrive and starting over, but I'd really like to avoid that. The computer runs great, plays games great, other than slow internet it works great. My computer is an AMD Sempron 3100+, EPOX motherboard, ATI Radeon 9550 video, has 1.5gb of ram, one 120gb harddrive and one 320gb harddrive. I went through the malware removal page on this site with nothing found or nothing changed. I'm open for any suggestions you may have. I'm stumped at this point. Thanks for your help. I've attached the logs from the malware page and Hijackthis. Thanks for your help.

 

What download speed should you be getting?

 

I have 5mbs service. Really the 4000kbps is pretty much what I typically get.

 

Does this still happen if only one computer is turned on and connected to the network at a time?

 

Not really sure, but I know my Playstation 3 is on the same network via wireless and it's just as fast as it should be too. I'll try shutting the other one down and see.