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I am fixing a desktop computer for someone and need to reinstall Windows. I need to know whether to install 64-bit or 32-bit Windows. They accidentally formatted the hard drive.

Normally I would just go into the hard drive and search for a Program Files (x86) folder as described here, but clearly that will not work in this situation.

So, is there a way, possibly with a Linux Live CD or maybe by just looking at the processor / motherboard, to tell if the computer supports 64-bit?

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up vote 4 down vote accepted

You can look up if the processor supports X64 or X86-64 by googling the processor model. It'll be a feature listed in the spec sheet.

If you boot the system with a linux live CD, then:

grep flags /proc/cpuinfo | grep lm

If you get any output, then the system supports Long Mode, or 64-bit addresses.

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If you try to boot off the 64-bit Windows installation disc, it will either succeed or fail to boot. If it fails, install 32-bit Windows.

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It should be easy to tell by find by looking up the processor.

Some CPUs such as Core iX are all x64, others such as Pentium 4 can be a little bit more tricky and you will need to know the exact CPU model, which should be visible via the bios.

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^That would probably be easiest vs. pulling the cpu cooler or having to boot anything else. Intel's ARK site: for when you have the model (assuming intel) ark.intel.com – nerdwaller Oct 31 '12 at 22:05

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