I seem to have this problem with all GOG games. How do I run this as a regular, non-administrator user under XP? It will install and play as administrator but not as a regular user. I've fixed this in other games by finding the game leaf in the registry and relaxing the permissions there but I that doesn't seem to work here.
Any ideas?

What account are you installing under?
If you've found the registry keys, you might be able to paste them into the HKey Local Machine folder instead of Hkey Current User, that should make them global.
if not, adding them to Hkey Users\ .default might do it

The installer requires administrator access. Nothing I can do about that. The only key, other than the usual GOG keys, I've found is HKLM/Software/Razorworks. I've relaxed permissions on it but that doesn't help. I'll try the HKU/.DEFAULT leaf.
Nope, HKU/.DEFAULT doesn't help.
A little more information. The error that pops up is:
"Unable to register APACHE HAVOC : DPERR_GENERIC"
A little searching tells me this is a DirectX error. Anyone have any ideas?