Why does grub2 write "invalid signature"?

Question

linux

The bios is password-protected on the netbook (you can’t reset it, you can’t find out the password) and there is no way to set boot from devices. The netbook is running debian wheezy. Tried to transfer control through grub to other bootloaders. I made a bootable USB flash drive with another Linux distribution, it loads normally through grub. If you write the path to the image in grub or unpack this image into a folder and set the path to it, then when you transfer control, it gives an "invalid signature" error. The image is definitely working, if you write in grub to boot the system from the image, it loads. But it does not give control to the bootloader from the image.
I write in grub
menuentry "Ubuntu Live" {
set root=(hd0,7)
chainloader +1 (or chainloader /isolive/isolinux.bin)
}

Answer 1

Did you look for engineering passwords for resetting BIOS on the Internet ??
Might not have to bother with GRUB
Take a look here:

http://yvision.kz/post/82503
http://white55.narod.ru/biospass.html
http://it-web-log.ru/2012/01/podbor-ili-sbros-parolya-bios/
http://habrahabr.ru/post/128466/
http://dogber1.blogspot.com/2009/05/table-of-reverse-engineered-bios.html

Or, as an option, brute force a password, I don’t know if it’s possible from under the OS, but it’s possible on Andruino)

http://hackaday.com/2011/11/16/brute-force-bios-hacking-using-the-arduino/