Which Window XP to buy?

All,
Pretty new with the Intel Mac, and planning on getting Parallels going on my desk IMac.

Down the road I will get a Macbook Pro and load Windows on it, using the desk for backup.

I'm going to stay with Windows XP (pro?), which one should I get that will work both on the desk and laptop? They have XP Pro, With SP 2, OEM copies which I have no idea what that is. And is the Home version much different?

Thanks.

You need to buy WinXP SP2 to be compatible.

OEM copies are ones made to be installed by the builder of the computer. Home version might be all you need but I would not run it on a pc as it has a lot less than the XP. Pro is not needed for just running parallels. After you explore a bit you might find you don't need it at all. I don't. I had to buy Quicken for Mac but have found open source or software preinstalled on my MacBook Pro for everything I need. As Schweb mentioned, make sure you get one with the service packs included!

You can use an OEM copy of Windows XP, providing that it is not a vendor-specific version. You can also use an older XP disc that doesn't have SP2 integrated and then later build an SP2 disc. The differences between XP Home and XP Pro are not important providing that you don't need to join a domain (rare for a home computer) and don't intend to use terminal services to remotely connect to your machine.

Technically OEM copies are licensed only for brand new computers