In my opinion, you should provide them with MPEGs. The company that I work for, we provide a 60 second mpeg clip that the affilliate can edit, as well as six(6) 10 second clips made from the same 60 second clip. Alot of MGPs require or prefer MPEG, and for those that don't, the affilliate can easily convert the MPEGs to WMV before they submit. Also, RealPlayer is pretty much outdated, so I wouldn't even bother with that format.

Oh, important note: File size is just as important as file length. The optimum file size for the 60 second clip is 6mb, and the optimum size for the 10 second clips is 1mb.