Boot Windows 7 iso from grub2

I want to do it because I want to install Windows 7 and my BIOS menu doesn't appear; it skips to grub2 menu at start, but that's another story... Is there a way to boot the Windows 7 installation iso directly from grub2?

Booting Windows XP with grub4dos

Booting the actual ISO with grub legacy or grub2 won't work, but with older windows versions (i.e. XP) it is possible to unpack the i386 folder from the ISO to the USB stick, and then use grub4dos to call the bootloader:

title windows installer via setupldr.bin
find --set-root /i386/setupldr.bin
chainloader /i386/setupldr.bin

or

title windows installer via /bootsect.bin
find --set-root /i386/setupldr.bin
chainloader /bootsect.bin

This might not work with newer windows versions or with newer hardware but there is also the option of..

Booting Windows 7 with grub2

With grub2 apparently something like this could work for Windows 7:

menuentry "Windows 7 (bootmgr)" --class windows --class os {
    insmod part_msdos
    insmod ntfs
    insmod ntldr
    ### A: either use this line or the next one, but not both
    set root='(hd0,msdos1)' 
    ### B: 
    ### search --no-floppy --set=root --fs-uuid ____INSERT_PARTITION_UUID_HERE___
    ntldr ($root)/bootmgr
}

Option A assumes your bootable USB stick/HDD is the first device and has a msdos style partition table. Adjust to match your configuration. If your boot device has a GPT partition table, then most likely you'll need to use (hd0,gpt1) (GPT in general is trickier to set up).

Option B uses the drive's unique UUID, which can be seen on Linux with sudo blkid or on OSX with e.g. diskutil info disk0s1 (or Disk Utility > Info).

The final entry might look for example like this:

menuentry "Windows 7 installer" --class windows --class os {
    insmod part_msdos
    insmod ntfs
    insmod ntldr
    search --no-floppy --set=root --fs-uuid 0E239BC6-F960-3107-89CF-1C97F78BB46B
    ntldr /bootmgr
}

Yeah, you'd think something like this would work:

menuentry "Boot Windoze" {
  search -f "--set-root /Winblows.iso"
  drivemap "/Winblows.iso" '(hd32)'
  drivemap '--hook' ''
  set root='(hd32)'
  chainloader +1
}

But Windows will just balk at that.

If you happen to have at least 4GB RAM, you can opt to load the whole DVD iso in memdisk and boot off that. To do that, download SysLinux and extract the memdisk file into your boot directory. Then you need to add code to Grub2 something like this

menuentry "Boot Windoze" {
  search -f "--set-root /Winblows.iso"
  insmod memdisk
  linux16 /boot/memdisk iso
  initrd16 /Winblows.iso
}

However, I'm not going to even test the code, as putting 3+ GB of data into RAM is just plain wrong (from an idealogical standpoint). No, I really wanted what you want, but in the end I put the Windows install on a partition on a USB using the Windows 7 USB/DVD download tool and chainloaded to that. Sorry there doesn't seem to be any other way that I can see.

Technically installing from windows's .iso file can't be possible. You can boot from the .iso using grub but after that Windows will loss contact with the mounted location or it is not capable of it. So both grub & Windows should aware of mount and boot. Currently Windows doesn't support.

So you need to extract/copy the content of .iso to root of a partition and then chain-load into it using grub.