It's built on Pro. WMCE
"Although Media Center is based on Windows XP Professional
, Microsoft has disabled its ability to join an Active Directory domain. This effectively precludes the use of Media Center in a corporate environment. Media Center still retains most other Windows XP Professional-specific features, such as Remote Desktop and the Encrypting File System."
"There are emerging a number of hacks that change the intended features of Media Center Edition. Among them include allowing the running of the Media Center Edition programs on non-Media Center Edition OSs, including Windows XP Professional and Windows Server 2003, to get an enhanced feature set otherwise not available with MCE 2005. There are also hacks that allow the joining of the domain at anytime"
Unless Pro doesn't work with gaming, WMCE works with it as well.