You need to head to neosmart.net forums to understand Vista/XP dual booting and drive letters better. Here's one of my posts from the neosmart forums about this issue. Hope it helps.
Vista XP Dual Boot - Understand the basics - The NeoSmart Forums
Hi All,
Now EasyBCD is a fantastic program. I have raved about it before and I will do it again. Vista has a powerful bootloader but trust MS to ruin its usability. EasyBCD actually unlocks the full power of the Vista bootloader. It also makes grub on the MBR redundant - a god send for newbies - with neogrub as a file on your Windows. And you can boot OSX and PE too! Now thats super flexible for people like me who use it to boot Vista, XP, Ubuntu and OSX on the same hard drive.
I just bought a Sony SZ and it comes preinstalled with Vista Business and all the junk of the universe reducing this powerful computer to a pre 200mhz P2 with 128mb ram days. Since Vista is a confirmed dog the best thing you can do is put yourself out of the misery is to kill it and revert to XP.
Alas not an option till sometime ago however luckily Sony succumbed to consumer demand and posted all XP drivers and utilities for SZ. I thought it will be safer to dual boot untill I can confirm all the stuff is working well on the notebook. This is not a dual boot guide, there are many of those around, just a little background information that will hopefully give you a little more information about Vista/XP bootloaders, how they work and dual boot systems.
Dual Booting Primer
There are 2 parts to the boot process, the bootloader and the files on the 'active' partition it looks for to boot the OS.
1. For XP this is the XP bootloader (which gets copied to the MBR of your hardisk) and these 3 files; boot.ini, NTDETECT.COM and ntldr.
2. For Vista its the Vista bootloader and the folder /boot on the root of the Vista partition and the file bootmgr also in the root which is the Vista boot manager.
3. The PC bios loads the bootloader from the MBR. The bootloader then loads the files it is associated with, IMPORTANT: The bootloader looks for these files on the 'active' partition.
(So if you have XP MBR and it doesn't find boot.ini, ntdetect.com and ntldr on the active partition it won't boot. Similarly if you have Vista MBR and it doesn't find /boot folder and bootmgr on the active partition it won't boot. This is usually the problem in some sticky dual boot scenarios, the files will be there but not in the active partition)
4. Vista's Bootsect.exe can write both XP and Vista bootloader to selected disk MBR.
for instance:
bootsect.exe -NT60 C: will write Vista bootloader to C drive.(you can write to any drive letter, you usually want to write to the active partition)
bootsect.exe -NT52 C: will write XP bootloader to C drive (you can write to any drive letter, you usually want to write to the active partition)
Now if you have these files with you preferably on a rescue disk like VistaPE/BartPE, and the knowledge of how they work you will never be stranded.
Easy BCD can also write the Vista bootloader but sometimes things are so messed you can't run it untill you use these tools first.
Dual-boot setup
Now installing XP after Vista has a few issues as opposed to installing Vista after XP.
If you install Vista after XP, Vista automates the dual boot and presents you with a menu to choose Vista or XP in the boot menu. You don't have much to do. Here XP is C drive(active partition). Vista would be any drive you installed it to, D,V whatever but not the active partition. Vista will install its bootloader to MBR and place its boot files in the active a partition, in this case C: where XP is installed. So when you reboot into XP you will see this new folder called /boot in your root and a file called bootmgr also in your root. The /boot folder contains a file called BCD which is what EasyBCD manipulates to set up boot options.
Now if you install XP after Vista, it will merrily overwrite your MBR with its own bootloader and the next time you reboot you will boot straight into XP. No Vista option. Installing XP after Vista also means Vista is the active partition and XP is installing on another partition/Disk, could be drive D/whatever. In this case XP will install to the particular partition you want it to but put its boot files in the active partition, in this case Vista's partition which is C. This is also why when you install XP after Vista in a dual boot system, XP drive will be D/or whichever drive you installed it to but not C. This is not really a problem, since XP is smart enough to set itself up properly but some installers can get confused and install on Drive C which is Vista.
Now a couple of things have happened in the background
1. Vista bootloader was installed on your MBR, it was referencing the boot folder on Vista drive C and bootmgr file on Vista drive C to boot Vista. XP just deleted Vista bootloader and placed its own bootloader which is now looking for these 3 files boot.ini, NTDETECT.COM and ntldr on the active partition to boot XP. XP install process places these files in the active partition, in this case C where Vista is installed not where XP is installing. So when you reboot XP bootloader reads these files from the active partition(Vista C) and boots in to XP.
To dual boot you have to:
1. Restore Vista bootloader.
2. Set up Vista bootloader to give you an option to boot XP.
Restoring Vista bootloader will boot into Vista, you won't have an option to boot into XP untill you set it up which is where EasyBCD comes in. Once you restore Vista bootloader with EasyBCD or bootsect.exe -NT60 C: you will be able to reboot into Vista. Here you can run EasyBCD to set up an entry for XP. EasyBCD will edit the BCD file and add an entry or XP. The next time you reboot you will have an option to boot Vista or XP and you are set.
But the whole problem for me was purely superficial. I didn't want XP as drive D, I had no intention of using Vista (just wanted to leave it there) and wanted XP as drive C. In my SZ following the normal dual boot guides XP was showing up as drive D. Apparently with some registry editing you can change that but it didn't work for me. XP doesn't like its drive letter changing after install and it won't boot.
So I reinstalled XP but this time after creating the XP partition in Vista I made it active. So when XP installed it installed on the active partition which is Drive C and after installation on reboot it showed up as Drive C which is what I wanted. But now restoring the Vista bootloader and setting up a dual boot would be slightly more tricky. Why?
if I restore the Vista bootloader when I reboot, the Vista bootloader will look for its files on the active partition, in this case it is drive C where XP in now installed (this is where Vista would be normally but remember I had made the XP partition active before rebooting to install XP) and will find no /boot folder or bootmgr file and no boot for me.
The trick for me now is to copy over /boot folder and bootmgr file from Vista's partition to XP and making an entry for XP via EasyBCD before restoring the bootloader. Once that is done Vista bootloader will find its files on my XP partition and offer me a nice dual boot menu. Of course the Vista bootloader files are also on the Vista partition but the vista partition is not active hence the vista bootloader doesn't reference them at all. Should I remove XP, I will have to make the Vista partition active and then reboot or else I will have a no boot show again. Hope this writeup will be helpful for those dual booting to understand how it works so you don't get into a sticky situation.
