UAC stands for "User Account Control".
Instead of running the installer or patch by double clicking, try to right click the file and choose "run as admin".
Also, after installing, you can edit you shortcut to ET by right clicking it and choosing properties.
Then go to the "shortcut" tab and click advanced.
Then select "run as administrator".
Not 100% sure that will work becasue i don't use UAC at all.