Rescue disk legacy bios does not boot/work

Avast Free Antivirus / Premium Security
1

I make the rescue disk on a uefi computer, I want the rescue disk for a legacy bios computer, so I uncheck the box to make one for legacy bios. It doesn’t work. The unchecked box should not take into account the choice of a rescue disk for legacy bios. The usb never boots on the legacy bios computer. The usb made with the unchecked box works on the uefi computer without disabling secure boot in the bios. This is proof that the unchecked box does not make a rescue disk in legacy bios.

The iso with the unchecked box only works in uefi not legacy bios.

2

Do you mean the other way around? So it shouldn’t make one for UEFI?

Depending on the age of the legacy computer it might not even be able to boot from USB.

3

Yes the reverse the unchecked box should not do for the uefi bios.
The computer starts other usb without problems including a ventoy with several isos. It is only with avast that it does not work.

4

OK. I’m not familiar with the Avast Rescue Disk. Hopefully another forum member can help you further.

5

What do you get when you try to boot? Avast USB does not recognized as bootable at all? Or any error message appears?

I tested iso/bios on Virtualbox and it can boot. If I enable EFI then it fails, so it seems it works like BIOS boot. What happens if you use another USB stick?

6

When I boot the usb I have the blue windows logo with 4 rectangles in the middle of the screen, the logo is not straight in the horizontal axis. It remains a few seconds/minutes and it becomes flat in the horizontal axis with the same transparent logo that covers it but not entirely, at the same time the computer restarts.

I tried another usb stick it does not work, and several usb ports.

7

So it means your machine recognized USB stick as bootable and try to boot from it, but something went wrong while booting. If UEFI-boot USB are used on BIOS-boot machine, it won’t even recognized as bootable.

In that case I can think of 2 possibilities:

  1. Corrupted installation. Files needed to boot rescue disk is somehow corrupted (not on USB stick but UEFI machine that creates it). In this case re-download needed files from Avast is the best option, but I don’t know how to do that other than re-install of Avast…
  2. Compatibility issue with targeted machine. Some machines has issues with certain OSes used in bootable USBs. Something like “Windows 7 based USBs are bootable, but 10 based one not”. BIOS tweak might help in some cases, but it depends.
8

Can you also not boot the rescue disk as an ISO from the Ventoy drive?

9

It doesn’t work on a ventoy usb stick.

All my tests without the box checked start on a uefi computer.

I’m going to reinstall avast…