"Vista is bit complex when it comes to sharing. The one key for XP is that you must share at least one folder for non-XP operating system to allow sharing of files.
Vista offers default sharing folder called "PUBLIC." This is similar to "Shared Documents" on XP. Make sure that XP is sharing at least one folder, i.e. Shared Documents, and do the same with Vista. Enable your sharing rights under Vista and see at least you have the chance to view networks around both computers.
To share printers, you must designate the printer to be shared by going to network connections > share files and printer. Enable your printer to be shared by going to Printers and Faxes and designate which printer (profile) to be shared.
At some incidences you may have to install network printer driver on your Vista machine (again, assuming XP machine is spooling for shared printer job)."