So, I've been digging into why Windows XP can't deal with a system clock set in UTC. Apparently, it even keeps its internal time as UTC, but it still won't deal with a system clock set to non-local time.
I found this article from an MSDN blog, which gives a decent summary of the reasons why. Basically, it would break support for some pre Windows NT/XP things. Well, XP and Vista already break enough other things compatability-wise that this shouldn't be such an issue now.
I also found this nice article on all the reasons it should be changed.
Apparently, a registry key does exist that once allowed people to use a system clock set to UTC, but it isn't documented, and most of the newer Windows code hasn't been updated to support it. No word on if Vista does a better job at this. Has anyone else had luck getting windows to cope with a UTC system clock?