Windows 7 installation on top of HP Windows 10?
 

I needed Windows 7 to be able to run a lordsmurf conversion workflow and ran into a couple issues while installing, so I wanted to post the fixes.

I more or less followed these instructions, which I believe were pretty solid. This site was also helpful.

I downloaded a Windows 7 Pro ISO and attempted to run the installer inside the ISO directly, but would get an error that there was a corrupt file. I then attempted to burn the ISO to a DVD thinking that would help, but it did not. To get past this issue, I did fix 1, listed below. I believe the file in question was winload.efi in one case and perhaps autorun.(not sure what extension...) in the other. Attachment IMG_3950.jpg shows the error encountered when booting to the DVD, I believe.

After fix 1, Windows 7 setup would run by booting to the setup DVD (although at this point I believe setup would have run by directly opening the installer inside the ISO), but it would hang on a Windows startup screen after one of the reboots. To get around that, I performed fix 2.

BIOS changes that fixed things (see IMG_3954.jpeg):
1. "Secure Boot": change to "Disabled"
2. "Legacy Support": change to "Enabled"

The warning in IMG_3949.jpeg regarding partition ordering did not seem to cause any problems; I ignored it.

Dual booting from a partition never works well. Not now, not 10/20/30 years ago. The only way to safely "dual boot" is to swap hard drives. But physical removal isn't needed, just use a switch like this: https://amzn.to/3IIs5Ji

I'm amazed how many viewed that Youtube video has. It's total crap, both quality and content.

If this is for a laptop, I'd again only dual boot if I had 3x drive slots, and could change the boot drive in BIOS.

In time, partition boot setups always fail. Always. Short term is fine, long term is a mess.

I use a desktop PC with 3 operating systems on the same hard disk (win XP + win 7 + linux) with no problem in switch between the OS's.
The multi boot is managed by GNU Grub, maybe this is the reason for proper operation in multi boot.