After installing Windows XP Service Pack 2 many fans of various peer-to-peer software will find that they no longer function. This is due to changes made to the TCPIP.SYS file in SP 2 effectively limiting the amount of connections a PC can make.
Quite why this change has been made under Windows XP is anyone's guess. A few reasons spring to mind though...
1.) Minimising the effect of SPAM sent out from hijacked computers
2.) Throttling peer-to-peer networks.
I've found a site that purports to have a fix for the problem, but I haven't tried the hack, although I've included the link if you are brave. (I will accept NO responsibility for any concequences of using this hack though.)
All this news will be a blow to the rising number of BitTorrent fans, who use it to legally download Linux distros and other open-source software.
Perhaps this will help Linux gain more ground over Microsoft's Windows?