I have a bootable USB stick for Windows 7 Professional x64 that contains an EFI boatloader (I think).

It's always installed 64-bit just fine but I tried using it on an older HP machine and it would only install 32-bit Windows.

I don't get any option to choose 32/64-bit during installation and always thought that it was only a 64-bit iso.

The only way I could get the ISO to install as 64-bit was to burn it to an ISO instead and to use that.

Why on this computer did it fail? The processor is 64-bit compatible.

  • Are you sure that it's a 64-it processor? If it doesn't show up as an option, it means 64-bit windows can't run on it. – rahuldottech Oct 31 '18 at 4:34
  • What CPU is in the machine? And what model machine is it? – Keltari Oct 31 '18 at 4:35
  • It's an Athlon 64 X2. Windows 7 will install as 64-bit if I install it from a bootable ISO but not from a bootable USB. – Zhro Oct 31 '18 at 5:05
  • 1
    We could do with some more information. E.g. 1) Is the USB stick EFI only (no bootsector, boot64.efi or similar installed on the ESP). or is it dual boot (both bootsector for old BIOS installs and a ESP)? 2). What is the firmware on the HP. Might be classic BIOS firmware. Might be EFI firmware *64 bits most of the time' or it might be the rare 32bit EFI version usually only found on some brand name computers. – Hennes Oct 31 '18 at 5:14
  • When we download Windows 7 image, we could just choose to download the Windows 7 x64, which will not contain x32. At least Windows 10 can did this. – Joy Oct 31 '18 at 9:38

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