Reinstalling XP, good idea.

Updating XP, bad idea in this case.
Since the problem seems to be DirectX 9.0c and/or XP SP2, the only way reinstalling will help if you revert to before the above versions of XP and DX, and then stay there.
EDIT: Wait a sec... he said OOTP5. Is there an "end-of-game sound crash" in v5 too?