In case all else fails, you can get the filenames and hashes of Technet released XP ISOs from
here. You can google a filename for various places to download it. It's not nicely fair and square the way a Technet subscription would be, but with the hash info you can at least be sure you're not getting all kinds of crap needled in.
Catilley - are you talking about OEM discs? I tried to sell an OEM disc of Windows on eBay many years ago, but Microsoft had the auction shut down because they don't allow resale of OEM discs. I'd be extremely wary of purchasing Windows discs from eBay.