>Now how do I know if the current user has execute rights on a certain executable?

knee jerk answer was going to be "NetLib" but Larry beat me too it =D)

Perhaps an alternative is a metadata approach to implementing internal security... users in a table with logical indicators of what they can and can not get at. Then tweak you loader app to do a lookup and conditionally handle things all inside your app. Prone to maintenance, but so is anything regarding application security measure when your dealing with it as an afterthought.