How would I synch the clocks of several non-domain computers

we have several remote sites , each has 2 or 3 computers not members of our corporate domain.  windows xp professional, there couple windows 2000 computers still out there.   had script run 'net time \\anothercomputer /set /y.   realized script although running not updating time.   ran manually, , received message... "access denied" 

i've tried making connection computer @ \\computername\ipc$ thinking may establish communication, doesn't seem help.  

i have tried calling internet time server directly, not seem help. 

has synchronized stand alone xp machine domain controller (in domain it's not member)? , if not, have suggestion how can sync of these machines single source. 

(if not correct forum, please me identify appropriate one.)

thanks in advance. 

i've used w32tm, windows time service, http://support.microsoft.com/kb/314054

cheers,
florian

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microsoft mvp - group policy (http://www.frickelsoft.net/blog)

Windows Server  >  Directory Services