256 MB isn't much if you also run a lot of apps. I've got one system with 256 MB of RAM, and 36 is available. If I were to fire up LimeWire, it would take more than half of this available RAM away too (Java = memory hog).

Using WinNT/2000/XP, when LW becomes unresponsive, right click on your taskbar and open up your task manager from the menu (if "task manager" doesn't show up, make sure you're clicking on a blank area of your taskbar).

Click the "Processes" tab and search for Limewire in the "Image Name" column. Might help to sort that column by clicking on the column-header.

Once found, right click on the Limewire entry, select "Set Priority" and then "Low".

Hopefully, this gives some time back to your CPU and LW will become responsive again.

P.S.: Sometimes you may seem not to run that many apps. Only explorer shows up in your taskbar. But with the above method, you can also see how many apps are actually running in the background (services, etc.) and how much memory they take - you'd be amazed.