OK, I need to correct a couple of comments on here before people get the wrong ideas.
First off, OEM software is less expensive because it is put out without manuals and such and is supposed to be sold only along with hardware. It was not put out to be sold separately. This does not mean you can't change motherboard or any other component of the system. You can even change the system you have the OS installed onto as long as it is only installed on one system.
I´m sorry to say but this is incorrect. From Microsofts own FAQ regarding OEM Licenses:
Q. My customer bought a new PC and wants to move the OEM software from the old PC to the new one. Can't users do whatever they want with their software?
A. The OEM software is licensed with the computer system on which it was originally installed and is tied to that original machine. OEM licenses are single-use licenses that cannot be installed on
more than one computer system, even if the original machine is no longer in use. The End User
Software License Terms, which the end user must accept before using the software, states that
the license may not be shared, transferred to, or used concurrently on different computers.
System builders must provide end-user support for the Windows license on computers they build,
but cannot support licenses on computers they didn’t build. This is a fundamental reason why OEM System Builder licenses can't be transferred.
Q. If my customer asks me to upgrade a PC with new hardware components, when is a new operating system needed? When would the PC be considered "new"?
A. Generally, an end user can upgrade or replace all of the hardware components on a computer —except the motherboard—and still retain the license for the original Microsoft OEM operating system software. If the motherboard is upgraded or replaced for reasons other than a defect,
then a new computer has been created. Microsoft OEM operating system software cannot be
transferred to the new computer, and the license of new operating system software is required. If the motherboard is replaced because it is defective, you do not need to acquire a new operating system license for the PC as long as the replacement motherboard is the same make/model or
the same manufacturer's replacement/equivalent, as defined by the manufacturer's warranty.
Source:
www.microsoft.com/oem/en/licensing/sblicensing/pages/licensing_faq.aspx#fbid=fYAFbhBonf2
Second: As far as going with Home Edition or Pro edition, it depends on your needs. If you have games or other software that won't run properly in Windows 7, the Get the Pro version as you can download Windows XP virtual for free from MS with Pro or Ultimate. You can't get it at all if you have the Home editions. This saves you from having to own an XP disk as well as a Win 7 disk and make your system dual boot or have 2 separate hard drives in order to play your older games.
With that said, there is something that helps out the home user on Pro and Ultimate. There are actually a number of things, but I am not going to list them here as that is a waste of time for me.
Quite correct on the virtual XP, forgot about that but probably because I´ve never needed it. On Home edition you can still set a application to run in compatibilitymode for XP, and while it´s not the same as running a virtual XP it has worked on everything I´ve thrown at it so far. But then again I don´t play a lot of really old games.
As far as other limitations there are a few of course, but none which I think justify the 2,5 x pricetag for getting Pro or even more for Ultimate, at least not as a gamer. But every man is entitled to having an opinion.