Try putting command.com on a floppy disc (if your pc has one) or maybe a cd mite work. Boot from that device. Command.com is the old dos. So try changing the working directory to C:\WINDOWS\system32\ and use reg.exe to remove real player from the registry @ startup. Note: When you run real player it always checks to see if it is added to start up registry key. If not it adds itself again. I have to conistantly remove it from start up.
I think this way will work. Try downloading a copy of DOS (hopefully containing command.com) from