Here's the situation. I have three computers in my apartment at the moment, two PCs running Win XP, and a laptop running Win Vista Business Edition.
I have set up a local network between the two XP computers, so that I can use the secondary one as file storage. This connection went smoothly and without problems. My girlfriend's laptop (The Vista machine) however, is another story. Following an online tutorial, I have the Vista computer set to the same Workgroup as the two PCs. From there, I turned off the firewall and restarted the laptop. It is set to a private network. According to the tutorial, it should now be connected to the workgroup/network, but neither of the XP machines will recognize it, and we cannot find anything on the laptop that will locate or recognize either of the PCs.
I've already tried all of the obvious solutions, i.e. restarting, RTFM, and googling, but have had little success.
The most progress we've had thusfar is getting the laptop's name to show up as a potential network connection, but apparently neither computer has permission to access it. Any advice would be appreciated.
Alvin: The computers are all up to date with the latest service packs and drivers.

Gerry: I don't know if you misunderstood my problem, but this answer doesn't seem to have anything to do with it. Neither of the working machines have the same user name or password, and for that matter, the user names aren't even similar. I'm not having any kind of issue getting the systems to share files, I am only having a problem getting the Vista machine to recognize the already existing, functioning, workgroup. User accounts have nothing to do with this problem.
Upon testing the user name theory, I found no success. I switched all three systems to the same user name and password, and nothing was achieved.

The most important thing is to have the same user accounts on all the machines and the same passwords. This is key. The machines will use the account names and passwords to see who can access shared folders.

Make sure you share folders on the drives. Right-click them and select Sharing from the popup. Add the names of the other user accounts who will have access to them.

hmm... i had the same problem, but with vista desktop and xp laptop. Are your xp pcs up to date? (service pack 3)

the problem with my pcs were that the xp needed this update:

http://www.microsoft.com/Downloads/details.aspx?familyid=4F01A31D-EE46-481E-BA11-37F485FA34EA&displaylang=en

try that. hope it helps