Dual-booting XP and Vista and Order of Installation

[spacesurfer]

There are lots of questions about dual-booting XP and Vista. More questions arise when one of the partitions go corrupt because you can’t load an OS.

Vista Boot Disk

Here’s how to prevent something disastrous happening, like not being able to load either OS because you formatted an active partition: *** Create a Vista Boot Disk ***

The boost disk will allow you to boot Vista and/or XP if your MBR is corrupt or you lose your active partition, which contains your boot manager.

Active Partitions

An active partition is the partition that has Microsoft OS (XP or Vista) boot files. If you only have one OS, then your active partition will be your OS partition. You can only have one active partition. Therefore, if you are dual-booting, then one of the two partitions will be active. The order of install does not matter which partition will be active—meaning, if you installed Vista after XP, that doesn’t mean Vista’s partition will be active.

To figure out which one is active, right-click on My Computer, manage, under Storage, go to Disk Management. It shows all the volumes (i.e. partion is MS speak) and one volume will be active.

Boot Managers

In XP, the boot manager (also an OS loader) is a file called ntldr. In Vista, the boot manager is called bootmgr (but the OS loader is winload.exe). When you dual-boot, both of these files will be in your active partition. Ntldr cannot boot Vista. Therefore, the system will load the boot menu using bootmgr, which can load ntldr if you want to boot to XP. Your MBR points to your current boot manager. Thus, whichever OS you installed last will determine your current boot manager. Therefore, if you install XP after Vista, then your boot manager will be ntldr. So, you can’t boot to Vista since ntldr can’t boot Vista. Therefore, you should install Vista after XP to avoid repairing the MBR using Vista DVD.

Setup Behavior

So, if you have XP installed currently on C, then C most likely your active partition. If you decide to install Vista from within XP, then Vista setup will not change your active partition. Instead, it will add it’s boot manager (bootmgr) to C and take control from ntldr. Thus, Vista can boot itself and XP via bootmgr. Your Vista drive will be something other than C since it’s already taken by XP.

I believe, if you install Vista by booting from DVD instead of from within XP, then it will make Vista’s partition the active partition. I need to confirm this.

If you have Vista installed currently on C and decide to add XP, you will have to setup XP by booting from XP CD. (For obvious reasons, you can’t do it from within Vista.) Therefore, when you do this, XP will override Vista’s bootloader and you will not be able to boot Vista. However, you can continue XP setup. Once finished, then you can use Vista DVD to repair the MBR. The CD will make bootmgr the controller and you will be able to boot both XP and Vista.

I haven’t tried all of the following scenarios, but they should work theoretically. If someone wants a similar scenario for their system described here, then please try and post your results.

Scenario 1

If you want to have XP on C and Vista on D with Vista partition as active partition, then install XP first, making a C partition and D partition from XP’s setup. XP setup will make C the active partition when you install it. (You can also create D after XP setup in finished from Computer Management). Install Vista by booting from the DVD (not from within XP). Call up WinPE command prompt. Use diskpart to make D partition active. Resume install of Vista to D. Of course, C and D can be anything you want.

Scenario 2

If you want Vista on C and XP on D with C the active partition, then boot with XP CD, create C and D from XP setup. Install XP on D. D will be active since it’s the only OS right now. Boot with Vista DVD. Start WinPE command prompt from setup. Use diskpart to make C active. Install Vista on C.

It’s always best to install XP first since it’s the older one and ntldr will not load Vista. Installing Vista will override ntldr and make bootmgr the controller and it’s compatible with XP.

Grub

Both ntldr and bootmgr are not very good boot managers, in my opinion. Grub is a good alternative which does not change the MBR. If you want to use Grub, the guide is posted here: Dual-booting XP/Vista with Grub.

After reading the post, basically what you need remember is: make a Vista boot disk for backup, install XP then Vista, then boot to XP, rename bootmgr to bootmgrv and rename grldr to bootmgr, then copy bootmgr (grub in disguise) to where Vista’s botmgr was. This will allow you to boot to grub first.

Edited April 11, 2007 by spacesurfer

[aspenjim]

I just had this happen. So far it's costed me 2 of my technet volume license's. I thought I was gonna have to reinstall vista yet again and have it come inactivated and have to burn a 3rd. (Hopefully if the system works like it should, those should come available again in 6 months).

What is the command to repair the mbr from vista? Also, how do you install the command console with vista?

[spacesurfer]

Vista MBR is repaired from Vista DVD.

The Command Prompt can be called during Vista setup. It's WinPE's command prompt.

Check out the guide here for details on how to call the command prompt.