Maureen,
To allot more memory to a program: Click on the LimeWire application (the original, not an alias) Don't open the application, just click on it once to highlight it. Then click on your File menu (at the top of the screen) and hold the mouse over: Get Info (another menu will pop up) from it, choose: Memory.
A window will come up showing: Suggested, Minimum and Preferred size for that application. You can change the minimum and preferred sizes. I have mine set to 60000 K. Some recommend only setting it to around 10000 K. Either way, LimeWire will use as much memory as it wants but it will work better.
It still has its problems, but it will work faster with more memory allocated to it. I am using a Mac G4 OS 9.1 with 384 MB RAM. It came with 128 MB and I purchased an upgrade of 256 MB only so I can run other applications at the same time as LimeWire. I usually don't because of conflicts, but it's possible. By the way, you can purchase a memory upgrade anywhere. You don't have to purchase it from Apple. I think I spent $39 at Costco. I agree: Apple charges enough for their products!
Good luck. If you have any more questions, please post back.