Chris Wolf and MCPMag.com help answer the question, how do I prevent duplicate Virtual PCs from using the same MAC address?

I have a 150 PCs running Windows XP across three VLANs connecting to Active Directory on a Windows 2003 server. Each PC runs Microsoft Virtual PC with a Windows NT 4.0 image connecting to a domain on a Windows NT 4.0 Server. DHCP is running on the Windows 2003 server with a different subnet for each VLAN:

VLAN 1 = 10.143.47.0
VLAN 2 = 10.143.35.0
VLAN 3 = 10.143.34.0

DHCP has been set up with a range of 200 IP addresses in the pool for each VLAN with an 8-hour lease. With the VPCs running, VLAN 1 is running at about 70-percent capacity, VLAN 2 is running at around 50-percent capacity and VLAN 3 running at 20 percent.

The problem: Some PCs are unable to obtain an IP address from the DHCP server. We can fix this by recreating the VPC.vmc file or by editing it and removing the MAC address, but then another Virtual PC will have the same problem. We fix that and another will not connect; we fix that, then the first won't be able to get an IP address and so on.

The XP host PCs never have any problems connecting. We don't have any problems joining the NT VPCs to the domain when we first set them up.

Check out Chris Wolf's solution, here.