the workgroup name doesn't matter, well at least not for me. the first thing to check is to make sure the PCs can ping each other, if they can then you can try and access one of them through the other. each computer has a hostname that you set at install time and change at anytime, let's assume you have hostnames assigned like this:
ComputerA's hostname: "ComputerA"
ComputerB's hostname: "ComputerB"
If we assume ComputerA has w7, from Computer A click on start button, and on the search/run box, type "\\ComputerB" , then hit enter. this will try to open up the shared folders on ComputerB. you might need to type a username and password if it's needed.
If we assume ComputerB has WinXP, then from computer B click on start button, and then click on Run, this will open a box, in the box type "\\ComputerA" then hit enter. this will try to open up the shared folders on ComputerA. you might need to type a username and password if it's needed.
You can also use the ip addresses if you want, for example if computerB is 192.168.1.103, then you can type "\\192.168.1.103" in the search/run box. if you want to know the computer's current UP address just type ipconfig in the command prompt.
If your not sure of the hostname, there is many ways to find out the current hostname on the machine, the quickest is is to open a command window, then type "hostname" command, hit enter this will show you the current hostname.
if you see no shared folders on the other computer, this means you have not shared anything yet, so just go and share a folder on the computer you wish to share, usually by going to the properties then the share tab. but sometimes sharing is not installed by default and you may need to run a wizard before it's available.
If computers don't see each other, there is many possibilaties, but most likely is that they don't share the same subnet and without a proper gateway, also it could be due to a firewall setting.
