Windows 7: W7 laptop prints to XP desktop - but XP desktop not shown on network

This used to be fine:

But now, on the Windows 7 laptop, when I select "network" in the file explorer, only the Windows 7 laptop shows along with my router.

My XP desktop has the printer connected and I can print to it from the Windows 7 laptop just fine.

On the Windows 7 laptop, clicking on "network" used to show both computers.
Clicking on the XP would show the connected printer and shared folders.

Both have same Workgroup name and on the Windows 7 "Home Network" is selected as it always has.

EDIT - 12/06/12
Today, after coming out of hibernation, the XP now shows in under "network" in file exporer.
Prior to this happening, you could go to "add printer" and see the printers listed on the XP.
Also, as I said above, the you could always print to the printer on the XP from the Windows 7.
So is this 'solved' or still a mystery??????