You're not really supposed to be able to buy an OEM XP separate from the computer, so even if they're on "genuine" disks those are probably somewhat suspect. If they're leftovers from a builder who went out of business, they could be technically legal; but there's no builder to supply tech support, so they should be cheaper than usual. Microsoft won't provide tech support for OEM versions.

Lots of OEM builders make fairly significant changes to the OS to suit the particular hardware they're using and/or just on "whims and fancies," so "escaped" copies may not be plain vanilla XP.

Academic licensed XP copies are rarely seen here, so far as I know. The local college book store doesn't generally stock them. If you do find them, they'll likely be the FRP package at about 30% off(?).

Academic Office programs are more common, but I have no idea what the discounts might be.

The best deal is the Microsoft Employee discount rate which runs about 10 cents on the dollar; but they won't give that even to in-house contractors or temp employees.

John