There's a couple different ways to do it. From your desktop go to Start>Set Program Access and Defaults>, tick Non Microsoft and by "Media Player", choose RealPlayer from the drop down menu and click OK.
Or you can open your saved folder outside of limewire. The easiest way to do that is to go to the Library page in Limewire, hi-lite the saved folder and click the "Explore" button. Once it's open right click on the files you want to open with RP. Then click on properties and go to "Opens With" and click change. Then pick the player from there.
Read through this thread for more info:
http://www.gnutellaforums.com/showth...ded#post123227