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Difference between Windows Vista 32-bit and 64-bit
http://www.vistaarticles.com/articles/565/1/Difference-between-Windows-Vista-32-bit-and-64-bit
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Published on 05/11/2011
 
Finally, most versions of Vista are available in two further types: 32-bit and 64-bit.

Difference between Windows Vista 32-bit and 64-bit

Finally, most versions of Vista are available in two further types: 32-bit and 64-bit. These types refer to the way that the computer accesses its memory: older PCs were all 32-bit, but some modern ones can work in 64-bit mode. Generally speaking, it’s still best to install the 32-bit version on home computers, as this is compatible with more peripherals.

The advantage of 64-bit Vista is that it can use more memory: most versions of 32-bit Vista are limited to 4GB of memory, but if you want more, the 64-bit versions can use more than twice as much — if you can afford it.

Whichever version of Vista you choose — unless, of course, you somehow acquire a copy of Vista Starter — you’ll find that it contains useful hidden features that can make your computing life easier.