OK, not much info to go on but lets give it a try. New Dell computer probally came wit Windows XP MIN MEMORY 256/MB to preforme propperley, MS WORD 20/MB, LIMEWIRE lets say 50/MB there is 316/MB of your 512/MB most new computers come with extra programs loaded that run in the background such as Norton 30/MB when you add them all up you are proabbly pretty well maxed out on Memory 512/MB is pretty weak on a machine running XP. It will run XP and Office and maby a few other things but start runing other programs that consume memory and your computer will get slugish. Open task manager and see what else is running look at your total mem usage and you will probally find the problem. Add another 512/MB stick of memory you wll probally be amazed at the diffrence. Any way a little more info would be of help in the fueture such as

O/S 98/200/XP
Connection type Dial up/ DSL,Etc. and speed
Java Version
LimeWire Version
Ram 256MB/512MB
CPU Ghz
and anything you notice that seems odd

Latter Grandpa