[ Thanks to Steven J.
Vaughan-Nichols for this link. ]
“Why? As Faulhaber explains, “Computer viruses are very
confused by 64-bit. Taking a look at 64-bit executable code
detected by Microsoft anti-malware technologies in the past month,
the vast majority is innocent 64-bit files infected by 32-bit
viruses. While a 32-bit virus can only see other 32-bit processes,
it unfortunately can see the file system, and can tamper with files
it finds there.”“That’s the good news. The bad news is that this works only
because malware makers haven’t been targeting 64-bit Windows.
64-bit Windows XP and Vista both had stability problems and good
old regular 32-bit software often had problems running on it.
Because of this few people ran either one.”