Is that Norman or Norton internet security? If you're using such a firewall, make sure XP's firewall is disabled!

I know of a moderator on this site who gets just over 200 KB/s from the magnet link site. So ... why are your speeds dropping I don't know. It should have been reasonably consistent from that site. Have you noticed this happening downlding anything else not related to p2p such as software updates, etc.?

It might be modem related, it might be XP related, it might be ISP related. I'm not sure. I guess to overcome the XP issue if there is one with no. of connections, see http://www.lvllord.de/ or http://www.lvllord.de/?url=tools & consider downlding & applying the patch to increase maximum possible connections.