Another reason I dislike Vista is that on a Windows 2000, XP, 2003 system even if the system is not in your Domain or Workgroup - if you can supply the local system credentials and the firewall is not on or blocking you - it's possible to connect remotely and perform Administrative tasks. Vista does not allow that and will stop the attempt.
You may be able to do it with a WMI script (have not tried) but a normal

NET USE M: \\MACHINEx\C$ /U:MACHINEx\Administrator

does not work against a Vista box in my experience but does for the other OS versions.