What's a good rule-of-thumb for choosing between Windows 32 bit and 64 bit?

I'm installing Windows on an old(ish) machine again - and am again faced with the question of whether to install the 32-bit or 64-bit version.

Instead of asking this question specifically for some individual setup (like here), let me ask more generally:

What is a good rule of thumb, or combination of criteria or rules, for deciding between 32-bit and 64-bit?

Possible factors affecting the decision:

• Which version of Windows is to be installed (Win XP, Win 7, Win 8.1, Win 10); I'd guess the newer the version, the better it is to go 64-bit.
• Memory size (1, 2, 4, 8, more) - 32-bit prevents you from benefiting from > 3GB memory or so; and 64-bit must eat up more memory.
• CPU speed - is this at all a factor?
• Others, I'm sure...

Solution 1:

64-bit editions of Windows:

• are more secure, since they take measures against programs "patching" parts of Windows and enforce driver signing,

• unable to use 32-bit drivers due to the above,

• do not have the 4GByte RAM limitation of 32-bit editions,

• do not have the NTVDM that previous versions had, which allow running of old DOS applications, and allowing those applications to easily use installed printers and the network.

So avoid using 32-bit editions unless:

• your CPU is 32-bit and you have no choice,

• you have specific critical devices requiring drivers that will not work on 64-bit editions and you cannot get new drivers or new devices,

• really, really need to run old DOS applications under Windows, and something like DOSBox won't work (e.g. for printer or network support).

And @Geruta brings up a good point, XP 64-bit was not well supported by most hardware. XP is also a bad choice because it only supports 2 CPUs and many modern systems are quad-core. Of course due to XP being EOL by Microsoft and not receiving official updates, you should avoid really using it, no matter what edition.

Solution 2:

If you are installing XP, stick with 32 bit as 64 bit was more or less an after thought and driver support is nearly non existent.

If you are installing vista or higher, 64bit is preferable so long as your hardware can support it.

There is an argument to be made that if you have less that 4gb of ram that you should install 32bit as it won't benefit you. This is true, however, if you decide to upgrade your RAM in the future to anything higher than 4gb, your forcing yourself to reinstall Windows all over again. For this reason, I always suggest 64bit on any install that's vista or higher and the system can support a 64bit OS. Unless you have hardware or software that's been known not to work with a 64bit OS, I see no reason for not using it given the conditions above.