NTLDR controls dual-boot

After Windows installation, the Windows partition is marked active and the NTLDR can boot only Windows OS.

Boot from the GRUB floppy.

Setup GRUB into the boot sector of the Linux partition, say /dev/hda1

   grub> root (hd0,0)
   grub> setup (hd0,0)

Boot into Linux:

   grub> root (hd0,0)
   grub> kernel /boot/vmlinuz-... 
   grub> initrd /boot/initrd.img-...
   grub> boot

Copy the image of the Linux boot sector onto a new floppy (have the floppy formatted for DOS file system).

dd if=/dev/hda1 of=linux.bin bs=512 count=1
mcopy linux.bin a:

Reboot into Windows; start command prompt;

cd C:
copy a:\linux.bin .

Edit boot.ini and add another line:

c:\linux.bin="Linux Debian 4.0"