http://support.mozilla.org/en-US/kb/what-mozilla-maintenance-service
What is the Mozilla Maintenance Service?
Firefox now installs an optional service called the Mozilla Maintenance Service. This service allows Firefox to install updates without requiring you to click yes in the Windows User Account Control (UAC) dialog.
Note: The article only applies to Windows.
This article applies to Firefox 12 and above. The latest Firefox version can be downloaded from mozilla.org/firefox.
No UAC No UAC
on XP you get it to, I take it off I don't need if you got Windows Vista & Windows 7 keep you need it.