Sharing Files Between Windows 7 and Windows XP
Make sure both of the machines are on the same Workgroup which by default is named WORKGROUP.
From your Windows 7 machine, go to:
Control Panel > Network and Internet > Network and
Sharing Center
Now click on
Change advanced sharing settings.
Choose your desired options under Advanced Sharing Settings for the Home or Work and Public profile.
Now scroll down to the bottom of the list and choose
turn off password protection if you want to give access to all users to your public shares.
If you want to turn it on then only those XP machines users having a user account and password on this machine (Windows 7) can access shared files, printers attached to this machine and Public folders.
Save the changes if you made any.