Question : Explorer can't find network PC but Remote Desktop/ping can

I have 2 pc's on my SBS 2003 network domain (of 20 pc's) which can't have their drives accessed from explorer using \\pcName\c$.  I am a domain/local admin.  Those same pcs CAN be pinged and CAN be accessed through remote desktop using the pc names.  One pc has a static ip address and the other dynamicWe have flushed dns. We are stumped and would love some help. Thanks.

Answer : Explorer can't find network PC but Remote Desktop/ping can

Yes thanks, File and printer sharing is enabled.  And I found the problem...windows firewall was enabled and blocking things.