Installing XP on more than one machine?

Is there a way to install a single retail copy of XP (Home or Pro) onto more than 1 computer? I know there's a file that you can copy back into the System32 folder if you're reinstalling, but I'm not sure if that'll work. I had heard that after 120 days, the keys Microsoft gives you over the phone to activate Windows will reset, allowing you to use them again, but I don't want to wait if I don't have to.

Jaywalking is illegal and I'm pretty sure it's Pensylvania where women aren't allowed to drive a car without a person walking in front of the vehicle waving a flag and blowing a horn.

<font color=red>God</font color=red> <font color=blue>Bless</font color=blue> <font color=red>America!</font color=red>

Nope, neither Home nor Pro will let you do that.

I've bought Win 3.1, Win 95, Win 98SE, and Win 2k all in the last few years. But I own 3 computers and 2 of them almost always run a MS OS. Due to the fact that MS won't let XP be installed on more than one machine without purchasing another licence I decided to stop supporting MS because I simply cannot afford to buy more than one so I had to resort to finding a copy of XP online that allows me to install on as many machines as I like. I've had no problems with it what so ever and saved myself a few hundred $. MS thought they would piss off the crackers out there with their new OS but it seems they strive for this kinda stuff and the only people it really effected is the people who actually purchased their OS.

Well, they changed how they go about enforcing it.