0. Some general considerations, not limited to the version or 32/64 questions.
1. Microsoft has a lot of material. One could start here
, but it is a very general net to sift through.
2. Going through the sifter, one can arrive here
for a quick comparison overview. Check the tabs.
can give one a checking location for verified applications and hardware. Use the tabs.
4. There is a downloadable comprehensive Windows 7 Application Compatibility List here
. This XLS includes columns for both 32-bit and 64-bit systems. (I know of one niche program that is not on this list, but works fine on Win7 (friend's computer: bits unknown).)
5. The technology trend is toward 64-bit architecture. MS blurb
6. As I understand it, programs that are natively 64-bit cannot run on a 32-bit machine. 32-bit programs may or may not run on a 64-bit machine. Compatibility-mode (for older versions of Windows) may or may not be effective. (Not to be confused with XP-Mode in Ultimate.)
7. Drivers for hardware must be confirmed; check hardware manufacturer's sites for support of Windows 7. MS general statement is that Vista-compatible drivers probably will work in Windows 7. (My very, very limited experience is that: A) XP drivers don't, and B) compatibility mode doesn't help for old-Windows drivers.)
8. Decision reduces to
- will existing hardware and applications work
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