You do not have permission to access \\XPS Contact... Why not?

You have to understand how networking works when you try and to connect to a pc by name windows doesnt search for it but asks the Master Browser which has the list. It can take 15+ mins for it to update if a new pc comes on (thats 1 on the network that has been turned off and removed from the list). If the MB is turned off another takes over. You can run this scanner as it often wakes things up run it on several pcs and note who is MB http://www.nirsoft.net/utils/netbios_scanner.html

I have run it on all 3 and it shows that the XPS W 10 (which is fully connected to the COMPAQ W 7 and visa versa) is the Master Browser. The COMPAQ was the only one that reported it's self if that means anything.