It's simple, after you install OS what you want to do is disable simple file sharing on both XP Pro. Go to control panel/folder options, then click on the view tab and scroll down until you see "Use Simple File Sharing" make sure you uncheck this on both computer. I've made a list below you should follow if you want to get this thing working without a problem.
1)After the simple file sharing is disable you want to get the computers to access the internet, then right click on "My Computer" properties, go to computer name tab. Make sure both computer are in the same workgroup. Else click change and enter the same workgroup. Do this for both computer and restart both machine.
2)Open up command prompt, then use comp1 to ping comp2 and comp2 ping comp1. Example from comp1 pinging comp2 if comp2 ip address is 192.168.1.101, you can verify the ip address in the command prompt by doing ipconfig /all
ping 192.168.1.101
Make sure you get a reply on both computer, if not disable the windows firewall and any firewall or security program running. Then ping again and verify you get reply.
3)Go to control panel/Administrative tools/Computer management. Open up local users and group then select users. Verify that the Guest account is enable and not marked with a red x. Otherwise you will have to enable it, right click on Guest, go to properties and uncheck "Account is disable". Do this for both computer.
4)Go to control panel/administrative tools/local security policy. Open up local policies then select User right assignment. Search for the policy call "Access this computer from the network", double click on it, you should see the "Everyone" in there, if not you will have add it like in step7 if it's there leave everything alone. Now look for the policy call "Deny access to this computer from the network" make sure there is nothing listed there, double click on it and remove anything in there especially the "Everyone". Do this for both computer.
5)Go to your network connection in control panel. Right click on your local LAN and go to properties, verify File and Print sharing is installed in the list, double click Internet Protocol TCP/IP, then click advanced, go to WINS tab and verify that NetBIOS is set at Default. If not then set it and click ok to save. Do this for both computer.
6)If you made any changes from above make sure you restart the machines in order for the changes to take affect.
7)Now on the folder you like to share, right click and select "Sharing and Security". Go to sharing tab, check "Share this folder" and enter a share name if you have to. Now click on Permission, verify that "Everyone" is listed there. If not you will need to click Add, a dialog box will appear, click advanced then find now. It will list some users and group, scroll down until you see "Everyone", click on it to select it, press OK, then OK again, then OK again to get back to the sharing tab. Now go to the security tab, verify that the "Everyone" is listed there, if not you will have to do the same like the step in the sharing tab. After that leave the permission as it is and click apply and Ok to exit.
You should always restart after making a change. Now you should be set for file sharing if you follow these step. If you have any issue, let me know.