Windows 7 Laptop Can't "See" XP Desktop on LAN

I have an HP laptop running Windows 7 Premium Edition and a HP Desktop with Windos XP. Both are attached to a LAN. The laptop can be connected either broadband or wireless. The XP Desktop can see and access the Windows 7 laptop, but the laptop can’t access the XP. Ideas please

If you disable the firewall, can you see the Windows XP box?