take a snapshot of your guest while it is pristine
Ah; maybe I should be using "snapshot" instead of "clone" to revert back to virgin install state.
WXP clones nicely; I put together a nice, bare, XP system, and then cloned it to have one for AVR development, one for PIC development, one for TI development, etc... The W8.1 "clones" are the ones that won't "activate."