While downloading software on my desktop computer, it asked me whether you wanted a 32 bit version or 64 bit version. I do not know if my computer is 32 bit or 64 bit. How do I check it on a desktop PC?

You can check whether your PC is 64-bit or 32-bit from the System Specification.

Right-click on the Windows start. You will see the Windows start menu. Click the System from the menu.

You can read the system type (32-bit or 64-bit) under the Device Specifications.

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The System Type says 64-bit operating system. X-64-based processor.

So, I guess my PC is 64-bit.

Yes, your PC is 64-bit.