don't even bother with the software based stuff... If i'm not mistaken, Virtual PC is a requirement for XP Mode... microsoft tools with microsoft toys...
but looking at the AMD site (link above comparing processors) it looks like the 4400+ all have the same socket type.. so... i don't see a reason you'd need a new motherboard... or am i missing something?
Looking at the prices on Newgg.com, for AM2 socket type with virtualization... the price isn't that
Newegg.com - Yes, Socket AM2, Yes, Processors - Desktops, CPUs / Processors, Computer Hardware