Hyper-V Requirements
Hyper-V is similar to VMware in the respect that it abstracts the hardware from the vitrual machines. This is different from other products such as VMware workstation or Microsoft Virtual PC, where the VMs run on top of the host operating system.
Hyper-V has a few requirements to get everything up and running. First, you need to install Windows Server 2008 x64 (64-Bit). Other versions will not satisfy the Hyper-V requirements. The second requirement is probably going to be the biggest problem for people trying to run older hardware.
Hyper-V requires a processor that supports hardware assisted virtualization. AMD calls this AMD-V, while Intel calls it VT. Some older processors may support this with an update to the motherboard BIOS, others will not. I found that my 3-4 year old Opteron 165 did not support hardware assisted Virtualization. Some research will be required to see if your specific hardware is supported.