Theres a problem logining to the computer.........

My dads computer has Windows Xp Pro. installed on it...He
tryed to login but when he started his computer there was
no name to select and he did "CTRL+ALT+DEL" 2 times till
that other screen came up and he entered his password and
username the right way and it gave this error
message: "Your account has been disabled. Please see your
system administrator." He is the system
administrator....as i was saying before...there saying we
can't log in and theres no login name and we do not know
how to login. Please help.

Thank you

David