your ISP may be throttling p2p traffic. if that is not the case, try disabling and/or turning off ALL firewall software (including the built-in firewall with WinXP SP2). if you have a router, connect your computer directly to the modem without the router connecting anywhere to your computer.

after doing all these steps, get up and dance around your computer on one leg, then chant "this will work, this will work" and repeat. lol j/k

but anyways, now try connecting with limewire and see if you can reach your potential speed by doing a search that will return lots of results and download it just to test it. if its still slow, then chances are that your ISP is throttleing p2p traffic and there is nothing you can really do besides change ports on limewire to see if only certain ports are effected. after doing that, the only thing left to do is call up your isp.

if you DO get the speed at which your connecting to the internet at, then somewhere between your computer and the router is to blame. most notably is either port forwarding, and software firewalls to blame.