The first thing to do would be to browse through the other posts -- this is a common problem and has received answers here numerous times before.

1) Go to control panel "File Exchange" and change mp3 to iTunes. If Limewire ignores this, then

2) Go to versiontracker.com and get a little freeware prog. called "iTunes Associator", which will change creator and type of any file you drag to it to iTunes.