your computer sucks -- can't help you there
your intenet conenction sucks -- can't help you there
your ports are not set up correctly -- can help you here.
go into your router (usually just by going to 192.168.1.1 in IE/firefox). if you use a linksys router, you need to port-forward (under applications and gaming) ports 6881-6999, 90-91, 5000-5001. that will take care of all the popular trackers.
also, if yo'ure on xp sp2, with the winblows firewall turned on, you will need to "add a port" for 6881, on both udp and tcp, as well as 90 for both. you can get to that via the my network places.
Internet, not the best, but it didn't used to be this bad, so I think it is something that happened one of the thousand times I reinstalled. Anyway, I am using Linux right now (much better ), so I'll have to fuck with it later. I'll try changing the ports and seeing if that helps.