Hi,
As this problem crops up quite regularly I keep meaning to make a copy of this answer, so that I can paste it in instead of retyping it every time, oh well.... : )
Making the user a member of powerusers is overkill, as it gives them thetype of access to the machine that will allow them to inadvertantly wreck it (which is why the restrictions were put in place in win2k). Bear in mind that it's not just user error that can cause problems, if they activate a virus (for example) the damage it can do is limited by their restricted access to the system. Much better to only open the areas that the user needs to run the app. Go to www.sysinternals.com and download two free utils (sysinternals is run by some world reknowned windows experts so rest assured their software is safe to use). Their names are filemon and regmon. These utils in turn trace every access attempt to files or registry areas including the results of that attempt. log in as your user, use 'runas' to open regmonor filemon in turn with an admin account, and then run the problem app as the user (I usually do a test with only one of the utils running at a time to make life easier). Regmon and filemon will echo output to their respective windows. Once you havereceived the error message from the app, stop the reg \ file traces and scan the output for 'access denied' error messages. This will pinpoint exactly the files or registry areas that are causing the problem. Now open up ONLY those registry \ file areas to the user (or preferably a group). The result is a system that is still 'user proof, but which the app now runs on. Note that you can filter the output of the utils by specifying the name of the app which cuts down on the output to wade through, you'll be surprised at how many file \ registry accesses the OS makes a second. Good luck....