Simple filesharing is the only type of sharing available under XP Home. Make sure both systems are using it.
Open up My Computer and go to the Tools menu, then Folder Options.
Once there, go to the View Tab. At the bottom of the list of options, you'll see an option to enable or disable Simple File Sharing. Make sure it is enabled on both systems.
There are fundamental differences between Simple and Advanced file sharing - Guest account restrictions, passwords, shares too.
Here is a start,
http://support.microsoft.com/default...b;en-us;304040 .