I downloaded, mounted, and booted Debian's net installer ISO (e.g.,
https://gemmei.ftp.acc.umu.se/debian-cd/current/amd64/iso-cd/debian-10.10.0-amd64-netinst.iso and
https://gemmei.ftp.acc.umu.se/cdimage/unofficial/non-free/cd-including-firmware/bullseye_di_rc2+nonfree/amd64/iso-cd/firmware-bullseye-DI-rc2-amd64-netinst.iso)
in an old 64-bit W7 HPE SP1 VirtualBox v6.1 VM with a brand new virtual SSD (2 virtual drives = 1 old W7 HDD + 1 new blank SSD). I'm trying it before
doing it virtually instead of my real physical PC to learn and practice (don't want to hose my 12 yrs. old real hardware production PC!). I picked
most of Debian's defaults (no GUI packages to install for now). I'm currently having problems with its GRUB bootloader part. It detected Vista, but I
don't have Vista as shown in my https://i.ibb.co/ctfV40c/Grub-Vista.gif screen shot/capture. I have W7!

Thank you for reading and hopefully fixing it soon. :)

Ant <ant@zimage.com> (2021-07-03):

Hi Ant,

If you look at os-prober's code:
https://salsa.debian.org/installer-team/os-prober/-/blob/master/os-probes/mounted/x86/20microsoft#L26-60

you'll see that Windows 7 could be detected on its own, which I suppose
is not happening for whatever reason on your machine, but also that
Vista is the fallback (see “else” part on L51); another possibility
could be that the BCD indeed advertises Vista, even for Windows 7
installation, but I'm definitely not a Windows expert (nor do I want to
become one).

Either way, it seems to me your Windows bootloader has been detected
just fine, it might just get the wrong label in the end, but that
shouldn't be a huge issue?


Cheers,