i used to have that problem at college, system locked down, and no admin rights granted to users,
but i got round it by instaling portable apps on a flashdrive
and using that on the college comps.
its also good for on your home pc if you dont want to leave any nasty incriminating evidence on your pc, as everything is run from the flashdrive as though it was a seperate hard drive, not that i get upto anything dodgy lol
Mozilla Firefox, Portable Edition | PortableApps.com - Portable software for USB drives