Did you do a clean install of XP on this machine that used to have Vista? e.g., first formatting the hard drive? If so, that is super odd and, yes, I would expect that would be a hardware issue. Would be curious to see the dxdiag.txt files from all these machines to compare their hardware.

For info on how to generate a dxdiag.txt file:
www.empirisoft.com/support/showthread.php?t=75