how many windows 7 or XP nstalls on a license (boot camp and parallels)?

hi all.

i have a laptop and a desktop machine and have been using parallels on both of these machines for awhile.

i also installed windows 7 and windows XP as a BOOT CAMP installs on my desktop.

i just got a request on the laptop (where i have NO boot camp installs) to validate my windows 7 installation under parallels 8. this is somewhat confusing since it has been running on this machine for a long time at this point.

my question is that i am considering installing a BOOT CAMP installation of windows 7 or windows XP on the laptop or even installing a PARALLELS installation of XP on the desktop and the laptop.

does anyone know if there is a way to figure out in advance what is permissible so that i don't get caught at some point with an invalid installation? ideally i would like to have the XP and 7 BOOT CAMP installs and the windows 7 parallels installations (mac pro and macbook pro) and i'm wondering if i can install XP as parallels on both the machines or even do a BOOT CAMP installation on the laptop.

any advice and or facts on this?