A. Server 2003 uses different hardware abstraction layers (HALs)
for single processors than for multiple processors. Under
Virtual Server, the Server 2003 OS would use the single
processor HAL, and it will continue to use that HAL after
migration to Hyper-V with multiple virtual CPUs assigned to it.
To resolve this problem, you need to update the HAL within the
Server 2003 guest OS. See this Microsoft page for more
information on changing the HAL.