Give us some more detaisl. What did you do with the game before you tried testing it. What did you change from the last one you played?
Might it have to do with any scripts?
I just searched on rmxp.net, found this:
"Choose a different directory. You can't compile to root directories, only folders (not to C:\ but to C:\Gamegoeshere\)" in a post by DarkZero2840
Hope that helps some.