I do a lot of presentations on how to identify and fix "LUA bugs" in applications (*), both for Windows XP and Windows Vista. I frequently use a little VB6 application to demonstrate writing to various portions of the file system and registry, write to .ini files in protected locations, restart services, explicitly check for admin rights, etc. People have asked me to post that app to my blog so that they can use it too. So here it is, including the VB6 project/source code.
As is, no support, hopefully it's self-explanatory!
Chris Jackson has a more elaborate demo app with full lab script, geared toward application compatibility tools and techniques on Vista. You can get it here.
(*) "LUA" = "limited user account", a.k.a., "non-admin", "standard user"
"LUA bugs" = application or feature of an application that 1) works when run by a member of Administrators or Power Users; 2) fails when run by a standard user; and 3) has no valid business or technical reason for requiring administrative control over the computer.