The Zone

That's right, Windows 6 is the last Windows that will come in a 32-bit (x86) version!

In order words, future Windows will only come in 64-bit (x64).  No fret though, for 32-bit software can still run on 64-bit Windows, due to a built-in emulator.  However, if you have 32-bit software with 16-bit code, now that's a problem.

64-bit Windows can run 64-bit software and 32-bit software, but not 32-bit software with 16-bit code.

Likely this won't be a problem when the next Windows comes out years from now, for by then, it's likely all existing software will be updated to 32-bit at least, and it's highly unlikely 32-bit software with 16-bit code will be around anymore.

In the least, the problem would be computers with 32-bit processors won't be able to run post-Vista Windows.  So this means if you have the Intel Core Solo (single-core) or Core Duo (dual-core), you won't be able to run post-Vista Windows, for it's a 32-bit processor.  Only the Core 2 Solo and Duo onwards are 64-bit for the Core line of Intel processors.

On the Pentium line, only the 600 sequence of Pentium 4 processors, and the 800 and 900 sequence of Pentium D processors are 64-bit. The initial 500 sequence of the first pin-less (775 contacts) Pentium 4 processors are 32-bit.