Vista requires you to login to be able to access files, and as stated above most people use guest accounts as a way around this.
Depending on your router, you might not be able to use DNS for local traffic. Therefore try typing \\*IP address of other computer*. For example \\192.168.0.2.
If that works but you can't access the computer via its computer name, like for example \\computer, then DNS is not enabled. A way around this is just to add the IP address of the other computer to your host file.
Now if you do need to edit your host file, please be really careful not to delete anything, and make sure you spell everything right otherwise it wont work.
Open up C:\Windows\System32\drivers\etc, open up the hosts file in notepad.
you will see at the bottom of the document, 127.0.0.1 localhost, underneath that add in the details for your other computer.
For example, Underneath 127.0.0.1 localhost (on Vista there will be a ::1 localhost [This is for IP version 6] entry as well, just add it under that) add in 192.168.0.2 Computer.
If i was to type \\computer in windows explorer now, it will automatically take me to that IP address, which is 192.168.0.2.
You would need to set this up on both PCs to get this to work.
So theres a bit of info that might help. Remember changing the hosts files will only be useful if you can see the other computer by typing their IP address. If you can't access the other PC even when typing in the IP address you have not set up your network properly, you would need to go over your settings on each PC and find out what the problem may be. Might be file sharing is disabled, might be folder permissions, etc.
