I have a Dell desktop that's missing the actual Dell recovery CD. But it's got a legitimate XP Pro License key on the side of the case. I have a Windows XP Pro OEM CD from some other machine... Includes SP2, The CD has Part Number X10-59871 underneath all the Copyright Microsoft 2004 etc. (Around the center spindle, it says "X10-59896 (NM 05) 03") It's a legitimate XP Pro OEM CD. So I go to install the CD and it gets to the "Enter your Product Key" screen. I enter the key on the side of the machine... It does not work. So I google up some CD keys and get one that finally does work, then I follow the steps on here to manually change the Product Key. /how-to-update-and-change-windows-xp-product-key-manually/ I changed it to the XP Pro Product Key that it's supposed to be as shown on the sticker on the side of the case. Then I used the automated telephone activation system (Because I had not installed the Ethernet adapter drivers) and activated Windows... After installing the Ethernet adapter drivers, I started downloading the system updates... Of course the first thing that Windows Update wants me to do is run Windows Genuine Advantage authenticity checker program... Legit CD media used to install... Legit Product Key installed... It's no surprise that it checks out properly. The big surprise came when I let the screensaver kick in after it rebooted and sat at the login screen... It did not say, "Windows XP Professional." It said, "Windows Media Center Edition." Additionally, I can not install Windows Media Player because it's Media Center Edition 2002, not 2005. What happened here? How did I end up with an installation of MCE without an MCE disk? If I used an MCE Product Key to install, why did the OEM XP CD take the MCE key? Is there a registry key that I can change to get it back to XP Pro?