Following are the steps to get dual-boot working with GRUB; for more details you should go to the original source of this post. I used to install first Windows 2000 or Windows XP and use the Windows boot loader (NTLDR) installed in MBR to launch GRUB. Also, this should work on Windows NT (all 3 OSs use the same booting architecture).

1. Install GRUB on the first sector of the /boot partition. DO NOT INSTALL IT ON THE MBR!.
   If you are performing the Red Hat installation, for the “Boot Loader Installation” screen:
   

   • Select “Use GRUB as the boot loader”
   • Select Install Boot Loader record on “…First sector of boot partition”.
   • After finishing the Red Hat installation, reboot into Linux. If you don’t have a boot disk, try booting in linux rescue mode
   If you already have Linux installed:

   • Run the following command (e.g. assuming /boot is
     /dev/hda2): grub-install /dev/hda2.
     If you don’t know which partition contains /boot, run the df command and check the output.
   • Edit /etc/grub.conf and make sure there is an entry for your version of Windows.
2. Determine which partition contains the /boot partition by running the df command. You’ll see output like this:

   Filesystem 1k-blocks     Used Available Use% Mounted on/dev/hda3    8665372  1639580   6585612  20% //dev/hda2      46636     5959     38269  14% /boot/dev/hda6     513776   189504    324272  37% /mnt/sharednone          256624        0    256624   0% /dev/shm

   From this output, we see that /boot is on /dev/hda2.

3. Make a copy of the Linux boot sector onto a floppy or onto a FAT32 partition. We’ll name this copy linux.bin. To make a copy onto a floppy:
   • Mount the floppy drive if it’s not mounted (assumes /mnt/floppy exists): mount -t msdos /dev/fd0 /mnt/floppy
   • Run the following command: dd if=/dev/hda2 of=/mnt/floppy linux.bin bs=512 count=1
     Substitute the path for the if= parameter (the input file) with the appropriate partition from the previous step. E.g., set if= to /dev/hda2.

   To make a copy onto a FAT32 (vfat) partition:

   • Mount the FAT32 partition if it’s not mounted yet. If it isn’t listed in the df output, it hasn’t been mounted yet.
   • Run the following command: dd if=/dev/hda2of=/mnt/shared/linux.bin bs=512 count=1, substitute the path for the if= parameter (the inputfile) with the appropriate partition from the previous step. E.g., set if= to /dev/hda2. Substitute the path for the of= parameter (the output file) with whatever is appropriate for your system. The example here (of=/mnt/shared/linux.bin) is for copying onto a FAT32 partition called osshare.
4. Reboot into Windows
5. Copy the linux.bin file to C:\
6. Run notepad and edit C:\boot.ini. Note that C:\boot.ini is a hidden system file, so it probably won’t show up in Windows Explorer. To edit the file, try: Start->Run and enter: notepad C:\boot.ini. Add the following line at the end: c:\linux.bin=”Linux”. If your C: filesystem is NTFS (not FAT32), you must edit C:\boot.ini as a user with administrator-level privileges. To make C:\boot.ini writable, you can either :
   • Use Explorer:
     • Go to Tools->Folder Options->View and select Show hidden files and folders and deselect Hide protected operating system files (Recommended).
     • Right-click on the file, view the Properties and uncheck Read-only. You can now edit the file.
     • After editing the file, restore the settings to their original state.
   • Use the command-line:
     • Make the file writable: attrib -R -S -H C:\boot.ini.
     • After you’ve finished editing the file, put the settings back: attrib +R +S +H C:\boot.ini

7. Reboot again. You should be able to pick either Windows or Linux. Selecting Linux will start GRUB