Dual Boot Partition/Drive Switching

There is a lot to be said for dual booting operating systems, especially when one of them is brand new and you are likely to encounter a lot of driver and application compatibility issues with the new system. Such is the case with Vista. I had high hopes that software companies would have done a much better job with having stable, updated drivers available by the time Vista made its consumer debut. Sadly, that isn't the case with drivers or even full applications. The overall picture is really pretty bleak, and I'm not just talking about the smaller companies with limited staff. Many of the giants in the industry have made a pitiful showing in being ready for the Vista launch. All the more reason to dual boot, keeping XP as the primary and fiddling with Vista until it can be considered a suitable and stable primary system with a full compliment of Vista certified drivers and applications.

However, if you are going to dual boot you need to be aware the method selected for installing Vista can have an impact on how you interact with the hard drives and partitions on the system. Prior to Vista it was always a given that when you assigned a letter to hard drive or partition, that letter always remained a constant and pointed to the same place. That's no longer the case and you need to be aware of how the method you use to install Vista will impact drive letter assignments. It sounds more ominous than it really is, so take a look at the scenarios below and you'll be able to choose the method that best suits your situation.

Setting Up Dual Booting Environment

The screen capture below is Computer Management taken from an XP SP2 installation. As you can see, there are two (2) hard drives in the system (Disk 0 and Disk 1) as well as a CD/DVD drive. Disk 0 contains the XP installation on primary partition C: and I'm going to install Vista on Disk 1 Primary Partition D:. Actually, I'm going to install Vista two times using this exact same setup. The only difference will be where I start the installation. The first time I'm going to initiate the installation from inside Windows XP. The second installation will be started by booting the system from the Vista DVD. I have intentionally labeled the two partitions 'C - Disk 0 - XP Professional' and 'D - Disk 1 - Vista Ultimate' to make them easier to track in Explorer as the installations proceed.

Alright, at this point both of the Vista installations have been completed as I described above. The two screen captures below are of Windows Explorer in Vista. Remember from above, I said I intentionally labeled the two partitions 'C - Disk 0 - XP Professional' and 'D - Disk 1 - Vista Ultimate' to make them easier to track in Explorer. The (C:) and (D:) labels in Explorer are assigned by Explorer. This is where things get tricky with Vista.

Looking at the 'Install Started from Inside Windows XP' capture you can see the C: and D: drives are still labeled exactly as I labeled them originally. The only difference is that the DVD-RW drive has been changed from X: to E: and that was done by the Vista installation routine, not by any change I made.

Install Started from Inside Windows XP	Install Started from Booting Vista DVD

However, look at the 'Install Started from Booting Vista DVD' and you'll see things are different when the installation is initiated from the DVD. The partition that contains Windows XP still carries the original label I supplied (C - Disk 0 - XP Professional) but instead of being partition C:, it is now called partition (D:). The partition that I originally labeled 'D - Disk 1 - Vista Ultimate' has been renamed to 'Local Disk' and is now partition (C:). The DVD-RW drive has been changed from X: to E: and that was done by the Vista installation routine, not by any change I made. If you boot back into Windows Professional you would see that all the drive letters are exactly as they were before the Vista installations.

Why does this happen? Traditionally, the operating system has always been installed on the C: partition. Obviously this isn't an iron clad rule because you can plainly see that Vista can be installed on a different partition, in this case the D: partition. My guess as to why this happens is because there are a ton of applications written that are so poorly coded they have a hard time dealing with a situation where the operating system isn't located on the C: partition. So, Vista automatically switches the drive letters to eliminate some of these compatibility problems.

Is this is a good thing? I don't know if it can be classified as 'good' or 'bad' but it's certainly something you need to be aware of before you set up a dual boot installation. Personally, I find it annoying. I know where I installed something and I want the reference to those items to remain the same no matter what operating system I boot. If you want the drive letters to remain consistent across both booting options, select the 'Install Started from Inside Windows XP' procedure and you'll never have to deal with swapped drive letters. If you like the idea of always working on the C: partition, no matter where it is really located, select the 'Install Started from Booting Vista DVD' procedure.

Here is a real life example of how this 'feature' might play out when you install an application. Assume you are working in XP or in Vista installed under the 'Install Started from Inside Windows XP' procedure where the drive letters don't change. You start the application install procedure in XP and the program will likely want to install to C:\Program Files\~Some Directory~. If you are working in Vista, the application will likely want to install in D:\Program Files\~Some Directory~ if it is a well written application because it recognizes Vista is installed on the D: partition. If the application wants to install to C:, or worse yet, doesn't give you the option of installing to D: when you're working in Vista, I'd have serious reservations about using the application at all. It's poorly written and likely to cause other problems.

If you installed under the 'Install Started from Booting Vista DVD' procedure and the application says it will install to C:\Program Files\~Some Directory~, understand that what this really means is the application is going to install to D:\Program Files\~Some Directory~, but because the drive letters have been switched it appears to be installed on C:. Personally, I find this confusing and requires I be aware of whether the drive letters have been switched.

The Bottom Line

If you don't want to be bothered with the switching drive letters, choose to install Vista as a dual boot option using the 'Install Started from Inside Windows XP' procedure. The drive letters will remain consistent across both operating systems no matter which one is selected at boot. If you like the idea of switching drive letters automatically depending on which operating system is booted, select the 'Install Started from Booting Vista DVD' procedure when installing Vista in a dual boot situation.