Vista - Vista Premium 64 bit

Why does a certain software work for Vista 32-bit but not work with 64-bit version? Why is this difference in Windows and why does the software makers not make softwares for all versions of windows?

Think of the operating system (OS) as being composed of two primary parts:

1) The "privileged" portion.
2) The "non-privileged" or "user" section.

Everything that goes into the privileged portion must match the "bitness" of that OS installation. In other words, if you install 32-bit Windows, only software whose privileged-mode componentry is also 32-bit can run on that machine. The same holds true for 64-bit; if an application contains one or more privileged components (drivers), they must be 64-bit to run on a 64-bit OS.

In the non-privileged "user" section the situation is a little more complex. A 32-bit OS installation will also support 16-bit user-mode code (old installers are sometimes 16-bit). A 64-bit OS will support 32-bit user-mode software, but not 16-bit.

The ability for any given app to run therefore hinges on whether it contains privileged code - a driver. If not, 32-bit apps will run on 64-bit OSs, but not vice versa. It's analogous to the way that a DVD drive can also read CDs, but an old CD drive wouldn't know what to make of a DVD.

32-bit and 64-bit software are fundamentally different in ways which go beyond the mere number of bits. When developing software, there is some additional overhead (work) required to produce both 32-bit and 64-bit versions. It also makes testing more complicated for the developer because they literally have at least twice as many scenarios to test. Hence, if a developer feels there is a market for their product in both 32-bit and 64-bit versions, they will build both. Otherwise, they stick to 32-bit for older and smaller apps, or they go exclusively 64-bit for larger and newer products.

The days of 32-bit software are numbered. Within a couple of years, it may become difficult to find any new applications shipping in 32-bit versions. 64-bit has every advantage from a technical point of view.

One reason programmers do 32 bit and not 64 bit is because there are plenty of free or inexpensive 32 bit compilers and scripting languages with Integrated Development Environments(IDE) that make it easy to create programs(like drag an edit box onto a form instead of writing the code to implement an edit control.)

But there aren't many free or cheap 64 bit compilers and IDEs. It will happen in time but I don't think the software prognosticators envisioned the hardware changing this fast. Now if you spend over $300 at Best Buy you get a PC with 4 GB ram or more. 64 bit is going to happen faster than expected. I have to wonder if Visual Studio 2010 64 bit Express is in the works?