Error synchronizing with windows xp time service

I cannot synchronize my computer time with the windows time service.  When I try to sync manually, i get the error message "an error occured getting the status of the last synchronization.  The RPC server is unavailable".  I have tried various servers and nothing will work, i continuously get this message.  I am running windows xp sp2, any help or advice would be greatly appreciated.

 

E1705

2 gb core duo

2gb ram

100 gb 7200 rpm hdd

geforce 7900 gs