[Win7/VM-XP] Can't see Workgroup

[EE Win7/VM-XP]   Can't see Workgroup

I have a number of Win7 machines setup in a small peer-to-peer network.
They connect to a switch which connects to a router.
Connected to the same switch is a Vonage modem.

One of the computers serves as the fileshare host for the others (it does not run any server software). Let's call it PC1.

One of the other computers is also running VirtualBox/VM. Let's call it PC2.

Until yesterday PC1 could be accessed both from the Win7 side of PC2 and from the XP side. However XP can no longer see the rest of the network.

In answer to the obvious questions:
(1) Yes, all the computers (including the XP) are on the same workgroup.
(2) Yes, NetworkDiscovery is enabled on PC1.
(3) Yes, the VirtualBox guest is setup as BridgedNetworking  (/Devices/Network/NetworkSettings)

I am wondering if the problem may be related to the following.
We had to replace our router yesterday. As a result the Vonage device was no longer working (something do to with the firewall on the router). Tech support adviced to do the following:
(1) Rearrange the cabling so that the switch connects to the Vonage device, which in turn connects to the router.
(2) Configure the Vonage device so that it has a static IP address.  The static IP address entered into the device looks something like this

Regarding IP addresses:  

IPconfig on the XP side of PC2 shows:
(1) Ethernet Adapter LAN  IPv4 Address:

IPconfig on the Win7 side of PC2 shows something like this:
(1) Ethernet Adapter LAN  IPv4 Address:
(2) Ethernet Adapter VirtualBox Host Only Network LAN  IPv4 Address:

IPconfig on the Win7 side of PC1 shows something like this:
(1) Ethernet Adapter LAN  IPv4 Address:
(2) Ethernet Adapter VirtualBox Host Only Network LAN  IPv4 Address:

I notice that the subnet for the VirtualBox is different than Win7 and XP.
I don’t know if it's always been that way or not.

Anyways, could this be the problem??
If this is an issue, then why are the Win7 machines visible to eachother?
Any suggestions would be greatly appreciated.

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JohnBusiness Consultant (Owner)Commented:
Yes, the VirtualBox guest is setup as BridgedNetworking

But then the VM IP would be on the same subnet as the host machines and it is not. It appears the networking changed to NAT and if that happened when the sharing stopped, that would be the reason.
CE101Author Commented:
Hi John:

Thank you for the response.
In the meantime things were somehow resolved on their own.
XP can now see the rest of the workgroup.

Prior to this (for an unrelated reason) the router had to be reset and then reconfigured to allow access by the Vonage ports.  
So perhaps this resolved the issue.
Or perhaps it just needed numerous reboots of the computer.

Still doesn’t explain why XP behaved differently than Win7 during this period???

Thanks again for your interest in my ongoing tale of problems.

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CE101Author Commented:
See my previous comment.
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