When I first started getting everything together for the system I'm about to build, I was staying away from OEM parts. But when I was looking at a deal for Windows XP Pro, it said the OEM version comes in the original packaging with installation CD, microsoft profuct key, certificate of authenticity and manual. I was under the impression that OEM products do not come with a manual, so I wasn't looking for XP OEM. But, if the OEM version does come with a manual, what does it not come with? Is it simply extra software (like games i'll never play, etc.)? What's the difference between retail and OEM for Windows XP Pro? The price I found is $127.