If you are using Vista or Win 7, turn off UAC temporarily, see if that does it.
You do that in Control Panel > User Accounts.
How can I remove Adobe Reader? I use another PDF programme, and want to remove Adobe Reader but it won't let me asking if I have permission! My user account has me as administrator, but I can't get Adobe off my computer. I had the same trouble with my old computer and eventually removed it manually, but its still listed in the control panel add/remove and if I try to remove that it says it wants the installation disk!!