I recently used Microsoft Virtual PC on a site but ran into problems with bridged network cards amongst other small issues. I gave up on Virtual PC and thought my only other alternative was VM Ware Player which is free but I could’nt get VM Ware tools installed into my VMWare Virtual PC and VM Work Station is a bit expensive.
But then Virtual Box came to my rescue and has worked perfectly. And its free! I dont know how long it will remain free after Oracles aquisition of Sun.But hey its free now and a doddle to setup.
Shadowprotect images .spf and .spi files can boot up straight into virtual box as if they were a vhd or vmdk.
Here is a video tutorial on using Virtual Box from David Davis on Virtualizationadmin.com