have you tried safe mode? Also, try opening msconfig(start>run> type msconfig). If it opens, hide the MS services and disabled everything that remains and restart. if it works and you can install, then you either have a virus or some program is messing with things.
Yea, if the UAC is enabled try disabling it, restarting and try installing again. That should clear it up. Is this Windows 7/Vista? Make sure Windows update checks for driver updates by going to devices and printers, right click on the computer icon and click device installation settings and set to yesdo this automatically.
Other than that, you can try enabling the built-in Admin account: Start run, type cmd and press ctrl+shift+enter, then in the prompt type net user administrator /active:yes, press enter,(you can finish here or set a password by typing net user administrator *insert password here*, press enter. Log off and login to the Admin account using the password (if you set it) - there is no default password to the built-in admin account. And then try installing it there.
To disable the account simply type net user administrator /active:no.
go into controlpanel and search for UAC then turn it down all the way. It won't ask permission at all anymore. Another fix would be to make certain you ave the rights to do those things, are there other acounts on the pc?