The administrator account is the account that have the right to install/uninstall programms for all users.
It also have the right to modify any file and settings on the computer, especialy those that affect all users. It can also be used to create or suppress an account and change it's autorisations.
You need to enter the administrator password or log in as administrator, with the correct password, to proceede. If you can't, ask the person who have the password to do the cleaning for you.
Electro, September 2012