iTunes not working on x64 Windows XP

Sure. See the link in my signature.

For a blind guess, I would say make sure you have the 64bit version and not the 32. Using IE64 to download from Apple's site should ensure you get the correct version.
 
Or go to Filescrunch.com or Filehippo.com, and download the x64 version from there. Mine is already up and running.
 
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