Your company’s network has client computers that run Windows 7.
When a user attempts to log on to the domain from acomputer named Client1, she receives the following
message:
“The system cannot log you on to this domain because the system’s computer
account in its primary domain is missing or the password on that account is
incorrect.”
You need to ensure that the user can log on to the domain from Client1.
What should you do?

A.
Remove Client1 from the domain and rejoin Client1to the domain.

B.
Reset the account password for Client1 through Active Directory Users and Computers.

C.
Add the computer account for Client1 to the Domain Computers Active Directory group.

D.
Reset the account password for the user through Active Directory Users and Computers.

Explanation:
http://support.microsoft.com/kb/810497