I started using Hyper-V to build my reference XP images, and the reason for that - Hyper-V is the first hypervisor that uses the most typical HAL for modern computers - APIC. So, if you build your images on Hyper-V, there is no supportability issues and it works just fine. The problem is, that Hyper-V does not come with hyper-v NIC or VMBUS drivers, so I figured how to install it from the unattend.txt.
1. Mount C:\Windows\System32\vmguest.iso
2. Copy everything from it to your $OEM$\$$\Hyper-V-support\ on the distribution point
3. add lines to your unattend.txt