Problems running my media player under Vista

[Clay Clear]

My friend says my media player "locks up solid" when it's first run under Vista and he cannot do anything with it except alt-task manager out of it. We've been using my media player for a long, long time and this didn't happen until my friend bought a laptop with Vista preinstalled. My friend is above-average in hardware lore (he sometimes builds his own machines), but is basically an end-user when it comes to software, so it's not really an option for him to wipe his HDD and install XP Pro. I refuse to do it because I don't know how to bail out of any situation caused by Vista.

Any hints or guidance appreciated.

[Clay Clear]

BTW, the assistance I'm looking for is what in my media player could be causing this unusual behavior under Vista. I have no Vista machine to troubleshoot these kinds of problems, although my friend said he's willing to work with me to resolve the problem.

[Clay Clear]

Disregard my quest for assistance, at least for now. I recently discovered some code in one of my include-in-everything INC files that would screw up pretty much any of my programs when run on Vista, if this one numeric constant is set. My friend will be testing the corrected version of my media player tomorrow (it's after 22:30 hours here, now).