Did you actually RUN the XP mode? As a test, I installed Windows Virtual Server and XP Mode on a non-VT Intel chip (E5200). It installed fine, but it didn't run. Everything worked fine on an E6300, which supports VT.
There might be differences in our software platforms. I was using Win7 RC x64 on the E5200 computer.
When I start XP Mode in Win7 with E5200:
"Cannot start Windows Virtual PC Host process
Windows Virtual PC requires hardware assisted virtualization.
There is no hardware assisted virtualization support in the system."