You will get error message Error Message "Unable to Log You on Because of an Account Restriction" when you try to login to a computer using remote desktop.
Reason for this error message is the user account does not have a password. Simply login to the user account from the local machine and go to control panel > user account to setup a password.
Cool the problem will be solved.
how to login to computer using remote desktop. (windows XP)
Start > All Programs> Accessories > Communication > Remote desktop Connection
In windows Vista
Start > type "Remote desktop" in the search area. (I think thats coool and easy)