Or you could, you know, just comply with US and international copyright law, and also save yourself the risk of subtle malware, and get a legitimate OEM install disk. You get the media with OEM licenses purchased at Fry's and elsewhere. Get a Vista Basic OEM license that's 64 bit, and this can also be used to install other versions of Vista that you also have legitimate licenses for, and as an added plus, you get an extra license of Vista to use if you need it.
As far as I know, the above procedure is fully compliant with the Microsoft EULA and all applicable US laws, but IANAL. However one would think that they would not allow the OEM install disks to install different versions of Vista, if they weren't actually attempting to provide OEMs with media that could be re-used as needed to facilitate selling multiple copies of Windows.
You can also of course run a good quality 64 bit edition of Linux. SuSE supports 32 bit and 64 bit operation quite well with its x64 editions, and can be obtained free of charge, so if you're looking to add a 64 bit OS to your PC with a 32 bit Windows, you can go that route.
The vast majority of Windows software in existence is compiled only for x86, so having a 64 bit version of Windows, while allowing you to use more than 3.5 GB of RAM, will primarily be of use in allowing the simultaneous operation of multiple RAM intensive programs, so I see it being a legitimate solution for workstation users who have to run beasts like Microsoft Office and, say, Maya, simultaneously, but I see it being much less relevant for gaming, for now (although I suspect a lot of newer games have smart installers that can install 64 bit binaries, and that's a trend that will probably continue). That said, of the games I enjoy playing, most are 32 bit only, and many are 16 bit, so this of course if of no relevance at all to me.
