The message is a generic one that Windows regurgitates whenever there is problem accessing one PC from another, so it isn't very helpful.
Make sure you have at least one folder set as "shared" in the PC you are trying to access. By default, File/Printer sharing is disabled in XP but is enabled when you set a folder as "shared". Make sure that any firewall software is configured to allow access to networked PCs by entering their IP addresses in its "trusted" area.
You may have to have a User Account in the remote PC which has an identical Username/Password as that you have logged in to the local PC with. This normally applies to XP Professional, but may still be necessary. This is discussed in detail at click here