If I buy a copy of XP Pro, on how many PCs can I install it?

[ImmortalDragon]

If I were to buy 1 retail version of XP Professional, on how many computers can I install it legally?
If I'm only allowed to install it on 1 PC, what is the best option if I need to install XP Pro on multiple PCs?

 

[g-paw]

You can only legally run it on one machine. You're best bet if you can is to buy multiple licenses for the number of computers you have, otherwise buy OEM versions