How to install both 32 bit and 64 bit Windows on the same machine?

Both 32 bit  and 64 bit Windows will have to be installed in separate partition.

It does not matter which is installed first and on which partition.
But since Windows 7 64 bit setup cannot be started from within Windows 7 32 bit you might want to install that first.

If you already have 32 bit Windows 7 installed, you will need to boot up from your Windows 7 64 bit disk and click Custom Install in the install options to select the hard disk or partition where you want it to be installed.

Please the note that you will need 2 separate licensed product keys to accomplish this. 1 license for each.

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