Install Real Alternative (which allows WMP to play RM/RMVB files) and then run a reg hack so that you can see the files in MCE.
REGEDIT4
[HKEY_CLASSES_ROOT\.rm]
"PerceivedType"="video"
"Content Type"="video/realmedia"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Multimedia\WMPlayer\Extensions\.rm]
"Runtime"=dword:00000007
"Permissions"=dword:0000000f
"UserApprovedOwning"="yes"
[HKEY_CLASSES_ROOT\.rmvb]
"PerceivedType"="video"
"Content Type"="video/realmedia-VB"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Multimedia\WMPlayer\Extensions\.rmvb]
"Runtime"=dword:00000007
"Permissions"=dword:0000000f
"UserApprovedOwning"="yes"
Note that this does not allow you to view streaming media, only downloaded.

shipdriver
Kit: ThermalTake Tsunami Dream case, Intel 670 3.8Ghz CPU, Intel 915GEV mobo, 2GB DDR2-400 RAM, MSI RX800 256MB, 1x40GB WD SATA HDD, 1x250GB Maxtor SATA HDD, Lite-On SOHW-1693S ODD, ATI HDTV Wonder, Hauppauge WinTV-PVR-500MCE, Terratec Aureon 7.1 Space.