I previously mentioned that 32 bit Windows cannot access RAM more than 3.12 GB. Microsoft in an FAQ re the difference between 32 bit and 64 bit Windows says that 64 bit Windows can make use of up to 128 GB RAM.
Should you use 64 bit Windows?
The key thing for most users is be keenly aware of is that :
1. 64 bit Windows require 64 bit drivers, 32 bit drivers do not work.
2. Some 32-bit programs do not function in 64-bit Windows (Microsoft mentioned in particular that some antivirus programs might not work).
Dell for example does not allow purchase of Office Professional with Vista 64 bit.
I am going to purchase a new laptop when Windows 7 arrives and I will buy the 32 bit Windows.