Firstly, are both computers in the same Workgroup? The default for XP Home Edition is "MSHOME" and the default for XP Pro is "WORKGROUP". XP does support multiple Workgroups, but is is easier if your networked computers are in the same Workgroup and I'd suggest using a name of your own, not the defaults.
Secondly, when accessing network "shares" in XP *Pro*, it is normally necessary to be logged in to the local computer with a Username/Password that matches that of the XP Pro PC (or a User Account set up in XP Pro). More about that at click here
Any firewall software should be configured correctly to allow access to the networked computers. "Disabling" a software firewall doesn't always shut down processes running in the background and it can still be an obstacle to local network traffic.