Upgrade path to Windows 8 from Windows XP Professional, 64 Bit, Service Pack 2.

For "Upgrade" versions of Windows 8
You will have to reinstall your qualifying license (Windows XP, Vista or Windows 7),

Upgrading from:                      What you can keep:
Windows 8 Preview                   Personal files
Windows 8 Developer Preview   Nothing, but your old files will be saved in the "windows.old" folder
Windows 7                               Software programs; Windows settings; personal files
Windows Vista                          Windows settings; personal files
Windows XP                             Personal files

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System Requirements

    1 GHz processor
    2 GB RAM
    20 GB available hard disk space
    1366 × 768 screen resolution
    DirectX 9 graphics processor with WDDM driver

Additional Requirements to Use Certain Features

    Internet access (fees may apply)
    For touchscreen, you need a tablet or a monitor that supports multi-touch
    Microsoft account required for some features
    Watching DVDs requires separate playback software
    Windows Media Center license sold separately
    To access the Windows Store and to download and run apps, you need an active Internet connection and a screen resolution of at least 1024 x 768
    To snap apps, you need a screen resolution of at least 1366 x 768

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How to upgrade to Windows 8 and protect your investment
The steps you need to take to protect your current Windows XP, Vista or Windows 7 investment
http://www.pagestart.com/win8upgrdprotect102412.html

What are the cheapest and easiest upgrade paths to Windows 8
http://www.zdnet.com/what-are-the-cheapest-and-easiest-upgrade-paths-to-windows-8-7000005702/

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Microsoft details its Windows 8 upgrade plans - Source ZDNet June 28th, 2012
http://www.zdnet.com/blog/microsoft/microsoft-details-its-windows-8-upgrade-plans/13051?tag=nl.e064

Summary: Microsoft is getting closer to the Windows 8 finish line, and is finalizing details like its upgrade paths from older Windows releases to the coming version.

Microsoft has shared with select partners some specifics about what those upgrading to Windows 8 can expect when moving from Windows XP, Windows Vista and Windows 7.

•Users will be able to upgrade to Windows 8 (the name of the entry-level consumer version of the operating system) from Windows 7 Starter, Windows 7 Home Basic and Windows 7 Home Premium while maintaining their existing Windows settings, personal files and applications.

•Users will be able to upgrade to Windows 8 Pro from Windows 7 Starter, Windows 7 Home Basic, Windows 7 Home Premium, Windows 7 Professional and Windows 7 Ultimate while maintaining their existing Windows settings, personal files and applications.

•Users will be able to upgrade to Windows 8 Enterprise (available to volume licensees with Software Assurance contracts only) from Windows 7 Professional and Windows 7 Enterprise while maintaining their existing Windows settings, personal files and applications.

•Users will be able to upgrade to Windows 8 from Windows Vista (without SP1 installed) but only personal files (meaning data only) will be maintained. If upgrading from Vista with SP1, personal data and system settings will be maintained.

•Users will be able to upgrade to Windows 8 from Windows XP with Service Pack 3 or higher but only personal files/data only will be maintained.

What won’t work: Users won’t be able to upgrade or keep their Windows settings, files or applications if doing a cross-language installation. (However, users will be able to keep personal files/data during a cross-language install by using Windows 8 Setup.) Microsoft also is also not allowing users interested in doing a cross-architecture — i.e., 32-bit to 64-bit — install to do so. Whether running Vista or Windows 7, these users won’t be able to keep their existing Windows settings, personal files and applications or data. They won’t be allowed to upgrade this way, period.