Presuming that you have Admin rights, guess you must have to install Airn@v in the first place, then just remove IE7 using add/remove programs, the computer will revert to IE6, you can then use Airn@v normally. I have just done it on my laptop to prove it to myself.
Incidentally I have used Airn@v for years over a network, but putting a version on my home PC has been a revelation - really quick !