Well, first of all, I'm not going to answer your question about APIC
because I don't know the answer.
But if you want to install windows XP, and you don't want to use particularly
qemu as virtualizer, well I suggest VirtualBox, I installed both Windows XP
and Windows Vista, it seemed to me quite easy and fast (yet fast as a virtualizer)
Personally, I never succeeded in using Virtual Machine Manager with Fedora Core 8.0
I don't know why the new button doesn't work!!. However it seems that many use it