WHS - VMWare Server Virtualization
If you have not made use of virtualization, VMWare Server v2 is an excellent beginning factor. If learning and also convenience of usage is your objective, after that stick to Server v2. If performance is your objective, ESXi will certainly offer you extra as it does not have the expenses of the Windows OS needing to load right into memory and also CPU calls needing to be converted though the OS.
If your WHS makes use of RAID, you will likely shed it on ESXi as it is not likely that ESXi will certainly sustain your arrangement. I can be incorrect on this, so it is best to examine VMWare discussion forums.