Login in error message

Hi,
When i boot up my windows xp prof. sp1 (dutch) pc, and
fill in my username+password i get the following
(translated from dutch!) error message:

The Current time on this pc differs from the current time
on the network. Contact your administrator .....

What can i do to fix this? The Server where the xp pc
needs to logon to is a windows 2003 server.
I would appreciate it if one replys to my email adress.

Thanks
Oscar