First try downloading something from this site:

http://www.magnetmix.com/video.shtml

They are magnetlinks and should open up Limewire and start downloading at high speed (up to 200 KB/s depending on your connection)

If you get slow downloads from there it's either a configuration problem on your end or your ISP at fault.

If you get good speed from there then try reading through this thread:

How to find music Click me

If still no luck then System details - help us to help you - Link