Vista Can't Access Shared Folders or Printers on a Windows XP Computer by default.
Problem
Vista can't get to Shared Folders or Printers on Windows XP. I don't remember the exact error message but it's something like: "\\computer not accessible", or "Logon Failed: You do not have permissions for this type of network access". I've ran accross this a lot because people go out and buy a new laptop and it's running Windows Vista. Their desktop computer is running Windows XP and they want the Vista laptopto share files and/or printers with the XP macine.
Solution
The problem seems to be that Vista is trying to use the Guest account on Windows XP but this account does not have permissions to access the computer over the network. You need to enable the Guest account and give it Network Logon Rights.
Steps
On the Windows XP computer do the following.
Download and install the Windows Server 2003 Resource Kit Tools
Once installed click Start -> Windows Resource Kit Tools -> Command Shell
Run these three commands:
net user guest /active:yes
ntrights +r SeNetworkLogonRight -u Guest
ntrights -r SeDenyNetworkLogonRight -u Guest
If that does not fix your problem, try turning off all firewalls to make sure they aren't blocking the traffic.