I’m not sure a one-step conversion tool exists, but you can do two-step conversions.
The first step would involve VirtualDubMod (http://virtualmod.sourceforge.net) and convert the file from ogm to avi. You will probably be able to do a direct stream copy for video. For audio, if you have variable bitrate audio (such as ogg), you may have to recompress (to mp3 for example) because avi doesn’t support vbr audio.
Then for conversion to mpeg, use tmpgenc (www.tmpgenc.net) to convert the avi. For conversion to rm use helix producer.
How to convert from OGM to AVI or MKV to AVI with mp3 audio and leave the video source intact.
Download mencoder for windows, http://www1.mplayerhq.hu/MPlayer/releases/win32-beta/MPlayer-mingw32-1.0pre7.zip
Extract all files to a folder on your hd.
Open a Command prompt from Start->Accessories->Command prompt
“C:\Program Files\mplayer\mencoder.exe” “c:\video\video.ogm” -oac mp3lame -ovc copy -o “c:\video\videooutput.avi"