OK, WinXP successfully installed and is working OK (even though I've not done much yet). however, the system does become a bit slow, but so-far-so-good.
I am facing one problem though. I can use the mouse in the VirtualBox window (WinXP that comes up in VB) - the pointer moves OK, but everytime I click it wants to take a snaphot. There's actually pointers in there - one is just stuck