There's probably a converter program out there... But why do you have .rm files? I havn't seen anybody use that format for ages.
The dBpowerAMP Music Converter will do this. Just install dBpowerAMP which can be found here http://www.dbpoweramp.com/dmc.htm then install the proper codec for real media which can be found here http://www.dbpoweramp.com/codec-central.htm