I installed avast! on the x64 version of the Vista Beta 2 (Build 5384) and encountered the following problem: when I want to add the license key as a normal user an error message appears that says that only admins are allowed to do this. So I added it as an admin. But when I check it as a normal user again it does not seem to notice and only tells me that the demo time will end soon ???.
I would suggest that you uninstall avast using the same account that you installed it and then install it from ‘the Administrator Account’ and enter the registration key from the administrator account. That way avast should be available to other users.
Downgrading to normal user will mess the account, this is my personal experience.
avast does not work well in computers with more than one account with admin rights
Did you try to insert the key by click the avast tray icon, or by opening the About box directly from the main avast program (run e.g. from the desktop shortcut)?
I’m afraid that, due to the “UAC” feature in Vista, you’ll have to do it via the main program (the tray icon doesn’t have sufficient access rights).