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I don't recall doing anything exra for windows 2003 to set up a share. Double check to make sure the Windows firewall is off(well I always turn it off because it gives me more headaches than it relieves(that and I got a better firewall app anways)).
The fact that you can't ping makes me suspect it is a firewall type issue. However, remember, in an NTFS file system there are two sets of securities that must be set appropriately for sharing to work. You have the Share options and the Security; the more restrictive settings are applied.
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