FYI:
I normally log in as a non-admin account in win7, but when trying to update firefox it requires admin rights. I got around this by giving this user account control of the Firefox folder under Program Files. Then the update worked fine.. thought some may want to know.
Well, that punches a big hole in Windows' security gameplan, though. It's not an accident that a non-Admin (or a non-elevated Admin) can't mess with stuff in Program Files. For those of us using a Software Restriction Policy, it also opens a permanent loophole that anything could exploit, because it breaks the Catch-22 of SRP versus non-Admin execution privileges.
As a simpler workaround, how about right-clicking FireFox and using Run As Administrator from the right-click menu, then Help > About and run an update that way. Once the update is complete and FireFox re-opens, close it (to get rid of the unrestricted Admin privileges) and you're back in business.
If you're not using SRP and you really don't care if your program files can be freely molested by anything that wants to, then you could also accomplish the same thing by installing FireFox to the user's local profile. FF15 allegedly does include a fully-automated update mechanism, for real this time, so going forward it may be a non-issue anyway.
Would running the installer package as Administrator do this too?
Yeah, that works too.