No, not related to stability or reliability.
It says 32-bit (recommended)
so that for people who aren't sure what the difference means, they will pick 32-bit as the website doesn't know whether you are going to install on an older 32-bit only CPU.
In practice I'd guess CPUs in computers up to 7 years old would mostly be 64-bit even if the user has only had 32-bit Windows on them.
Much of the press coverage of 64-bit vs 32-bit implies that 64-bit is to do with using more than 4GB of memory, but this is mostly an oversimplification and a Windows-specific design choice for the desktop version.
* 32-bit hardware with PAE supports up to 64GB of RAM if the OS also supports it (36-bit addressing).
* 64-bit OSes can be installed on capable hardware regardless of whether you have 4GB memory, or less, or more. In 64-bit mode a CPU makes available additional sets of registers which well-written programs can take advantage of regardless of the amount of RAM.
* x86-64, AMD64, Intel 64 and x64 all refer to the same type of CPU architecture (and instructions sets at least in practical terms) that can run both 64-bit and 32-bit programs. A misconception is that the 32-bit code is emulated or virtualised which is not the case.
* IA-64 and Itanium refer to an Intel-specific architecture which is different and not compatible with x86.
There is a summary of AMD
CPU families that support 64-bit and some of them include older or low-end CPUs that you might not expect.
In any event one can download the 64-bit version as a LiveCD (or USB) and try it without blowing up the computer.
prompt $P - Invalid drive specification - Abort, Retry, Fail? $G
prlzx on n e w n e t: ADSL2+ / 21CN at 2.5Mbps / 800k
Edited by prlzx (Wed 21-Mar-12 14:26:09)