Win XP buying advice

It’s been many years since I’ve bought a new operating system. Like, er, 6 or so. I’d like to buy a legal copy of Windows XP Pro to upgrade my current OS, but everywhere I look online I find Dell versions or CDRs for sale, which I’m sure is going to screw me if I want to stay legal. So, can anyone point me to a place online that is selling legal, actual, factory-sealed copies of Win XP Pro OEM or otherwise for a decent price? Thanks.

Newegg.com has OEM XP Pro for 142.00 or XP Home for 90.00 the catch is you have to buy hardware to get it at that price ( MS rules) the good news is Newegg interprets that requirement very liberally so buying a 1.99 audio cable is “Hardware” as far as they are concerned.