"RGSS Player has stopped working" is the exact error. I've seen this error reported often.
Get him to open the Game.ini file and check what DLL it's referring to. Then get him to check that he's actually GOT that DLL. If he doesn't, he either needs to change the ini file to use the one he's got, or (probably preferable) get the correct DLL from the Enterbrain site.
If he's on Vista, also get him to right-click on the exe file, and change it to run as administrator, and to run in XP Compatibility mode.
I've seen all of these suggested as a solution to the problem. Make sure you come back and tell us which one (if any) worked