Looks like an intrepid haxor has dumped Vista on a MacBook by fooling Vista into thinking that the MacBook has a BIOS in there somewhere. The instructions are kind of convoluted but we encourage you to try this at home and confirm that it works. No screenshots, unfortunately.

Using the Bootable Acronis Disk Director CD on the MacBook, shrink the Mac partition. Create a new partition of type NTFS/HPFS in the remaining space. Setup a clean version of XP on a PC. Extract Boot.7z to the root drive of your XP installation.. So you have C:\Boot\ Copy bcdedit.exe to the root drive of your XP installation. C:\BCDedit.exe ...

[Thanks, Lukas]

UPDATE - This is theoretical and not tested and not real. And I was so excited.
Windows XP on Mac? [Neosmart]