There are 2 major bit differences in the editions of vista. Watch out for it.
If you purchased Vista Ultimate, the nice black box has both variants (32bit and 64bit) DVDs in it.
For the home and business editions, in the box, you get 32bit DVDs. However, i heard you do not need to pay for 64bit. In the box includes a toll free number which you could order for free. You might want to verify before you purchase it.
But in any case, you get both 32bit and 64bit by purchasing 1 edition.
Due to the limited addressing space, 32bit versions can only support up to 4GB of RAM.
Because of the extra 32bits, 64bit versions are able to support much more. See below;
128GB: Ultimate, Enterprise, Business SKUs16GB: Home Premium8GB: Home Basic
While for now 4GB might seem a lot for the average home user, but for IT Pro, 4GB might be a soon-to-reach limit. In the long run, 64bit is the way to go. Well, for now, i’m saving money for more RAM. Got quite a lot of virtual machine testing to do. The more ram i have, the more virtual environments i can run concurrently.