Good news for people who use Grub4Dos loader for multi-booting to various Microsoft OSes, including the new Windows Vista, and Linux. I've modified an old trick I've used to load Grub4Dos on system startup with Windows XP as the main OS. See the post at 911cd.net Multi-boot WinXP and other OSes with Grub4Dos for this method.

Background

For those of you not familiar with Grub4Dos (referred to as Grub henceforth), here's some background information on its benefits. Why use Grub instead of Windows XP boot menu or Vista boot menu? There are several reasons.

• You can't boot non-Microsoft OSes with XP/Vista boot menu. Grub4Dos loads Vista, XP, 2000, 98, Linux, BartPE on HDD or CD etc.
• You can't boot other devices, namely floppy and CD/DVD drive, from XP or Vista menu. Grub can boot floppy, bootable CD/DVD (even if your BIOS does not support it), and floppy images from its menu.
• It's backward compatible but not forward compatible; meaning, XP can load Windows 2000, 98, and other legacy OSes but not Vista. Vista can load previous ones but not future ones. This is not a limitation of Grub at this point.
• You can boot Windows PE 2.0 and VistaPE with Grub.
• Fourth, Grub does not modify the MBR or PBR. It requires no patching or hex-editing. It simply requires renaming a couple of files, which I'll explain next why renaming is required.

Why Rename?

My objective was to load Grub loader first, before XP boot menu (and now before Vista boot menu). In order to fulfill this objective, renaming two files is necessary.

You can add Grub loader to boot.ini so that you can get an option to load Grub in the XP boot menu. However, if you want Grub to load before XP boot menu, you'll have to rename two files. First, you have to rename ntldr (the XP loader) as ntldrxp and grldr (Grub loader) as ntldr. Basically, you are disguising Grub loader as the XP loader. So, the system thinks it is loading XP but it is loading Grub. Then, you can create an entry in menu.lst to load XP with the following lines:



If you had edited boot.ini to automatically load Grub without a timeout, then you would not be able to boot XP because of a circular reference. Why the circular reference? Because system loads ntldr, which reads boot.ini and loads grldr automatically (without an XP menu). Then, from Grub, you would choose to boot XP. However, ntldr will look for boot.ini and load Grub again automatically. It doesn't matter if you rename ntldr to ntldrxp. Ntldrxp will also look for boot.ini and you get a circular reference. Therefore, renaming both ntldr and grldr files solves the problem.

Booting Vista with Grub

So, with Windows Vista, is it still possible to get Grub to load before Vista boot menu? And can you boot Vista with a Grub entry? Both are yes!!

Even though Vista's boot process had been modified, the same trick works with Vista as with XP. Let's look at the differences between Vista and XP boot process before I explain how to get a Grub menu before the Vista menu.

For XP, the MBR looks for and loads ntldr. Ntldr then read from boot.ini. If it finds two or more entries in boot.ini, then it will present a menu option for the entries (unless you set to boot an item automatically). That's the process. (I've read that ntldr serves two functions: bootmanager and bootloader. As bootmanager, it presents a menu for XP and other OSes. As bootloader it itself can boot XP.)

For Vista, the MBR looks for and loads bootmgr. You can say bootmgr has replaced ntldr. However, bootmgr serves only one function: as a bootmanager. Bootmgr refers to a file called bcd (short for boot configuration data). You can say bcd is like boot.ini. It contains the menu entries for Vista's boot menu. There's a third file called winload.exe that actually loads Vista. This is the bootloader for Vista.

So, for our purposes, we need to replace bootmgr with grldr to get a Grub menu before the Vista menu. Then, we need to create an entry in menu.lst for booting Vista, XP, other OSes, and other devices. Finally, now for the instructions.

Requirements

1. grldr, the file that loads Grub loader. You can find it at http://grub4dos.jot.com/WikiHome. Download the zip file and extract files to get grldr.
2. WinImage or any other floppy image creator
3. Floppy drive and a floppy
4. A system that is currently dual-booting XP and Vista

Backup System

First step is to backup your system with System Restore or Vista's backup program just in case things go haywire (if you follow directions correctly, it shouldn't). I don't use system restore but you may want to. If you are comfortable, you can skip this step.

The worst that can happen with these simple instructions is you lose the ability to boot to either Vista or XP. If you created a Vista boot floppy as explained in the next step, then you should be able to recover. If something worse than this happens, you did something beyond these instructions.

Create Vista Boot Floppy

Now, make a Vista boot floppy. Follow the instructions: http://www.msfn.org/board/index.php?showtopic=95092. I advise you not to skip this step. It will not only help you now, but also if in the future you can't load Vista or XP, it will come in handy.

Note: you can create a Vista-only boot floppy, XP-only boot floppy, or Vista/XP dual-boot floppy by modifying your boot options in Vista. If you want a Vista-only boot floppy, modify your boot options to boot Vista automatically (without a timeout). If XP-only, boot XP automatically. If you want dual-boot, specify a timeout before loading your default choice. The changes you make are reflected in the bcd file. Therefore, all files will be same on these floppies except the bcd file. For the purpose of these instructions, you're better off creating a Vista/XP dual-boot floppy so you can boot to either one.

Rename bootmgr

After creating a boot floppy, boot into XP. Give yourself permission to modify bootmgr. You may have to take ownership. (I took ownership of the file and then modified permissions. I now realize maybe that was not necessary. Not sure.) Rename bootmgr as bootmgrv.

Rename grldr

Rename grldr as bootmgr. Just like in XP, we're going to fool the system into thinking it is loading Vista, but it is loading Grub loader. Then, copy bootmgr (grldr in disguise) to where the Vista's real bootmgr was, usually in the root folder of your active primary partition.

Create Vista Entry in Menu.lst

Just like how ntldrxp was able to boot XP, bootmgrv can also boot Vista from Grub menu. Create the following entries in menu.lst. The # indicates comments. Take a look at the comments if you are not familiar with menu.lst.



Note, we do not need to rename ntldr as ntldrxp in this case. You can also add Linux and other OSes supported by Grub. I don't use Linux. You can search for instruction on the net.

Reboot

Voila! Reboot and you should see Grub menu with your boot menu options!

Please post any discussion points.

This post has been edited by spacesurfer: Jul 11 2007, 05:52 PM