User account control settings.
file and registry redirection
If you override the User Account Control it allows an application to be run even if the you do not have the required administrative privileges.
Administrative.
Administrative privileges
Administrative privileges
Administrative privileges
Administrative privileges
You may not have administrative privileges.
As many as you have users with administrative privileges.
You can't. The only way to bypass access privileges without having administrative privileges is via bugs in a program already running with administrative permissions. Since most programs aren't (or shouldn't be) run with administrative privileges, you can't rely on 1.) a program to be running with high privileges, and 2.) for it to have unpatched bugs. If such a bug was known, it would become patched fairly quickly (at least in the case of Linux).
Enterprise Admin. Just a hunch.
Most applications written for XP will work perfectly fine on Windows Vista. The ones that don't usually either rely on an obsolete library, or require administrative privileges to run, which Vista no longer grants by default.