You can copy the saved Playlist in a external storage and when you re-install Windows you need to paste the save playlist to your PC. But make sure the path of the songs specified in the playlist and the path of the songs stored are one and the same.
Because Realplayer doesn't store the original content of the songs but only the address/location of the songs. If the songs is renamed or moved from the previous location, playlist will not play the songs. In that case, you need to remove the file to the original location.