Alright, let's start by explaining my setup. I have a single hard drive split into 4 partitions. C: D: E: R/X:, in this case. On my older XP install, this is how the drive letters are assigned: C: is the first partition and is used for storage, non bootable. (boot partition) D: is the third partition, bootable to XP x32. E: is the fourth partition, used for storage, non bootable. R: is the second partition, bootable to Vista x64. On my Vista install it is like this: C: is the second partition, bootable to Vista x64. D: is the first partition and is used for storage, non bootable. (boot partition) E: is the fourth partition, used for storage, non bootable. X: is the third partition, bootable to XP x32. The first and second partitions are primary ones, the third and forth are logical. I've been using it this way for almost 2 months. I've also been using ADDS 10 for quite some time, constantly doing partition resizing without any issues at all. (Never used the DD CD, have always done it within Windows) Looking at it from Vista's perspective, I was low on disk space on drive X: (3rd partition), where I install my games. I booted to X, in which X: became D: (XP's table above). I took space away from R: (2nd) and E: (4th) to give to D: (3rd), not a problem, right? Then I took space away from C: (1st) to give to R: (2nd), still not a problem, right? Everything went fine until I decided to boot back to my Vista installation. It got to 'preparing your desktop' and stayed there loading for quite a while. Eventually it got to what was supposed to be my desktop, though it was just a Windows 95 looking blue background. A while later a window popped up saying something about rundll32.exe, blah blah. After that it asked to restart the computer to apply changes. I rebooted. Upon rebooting, the same thing happened, just a blue background. It stayed like that until I couldn't wait anymore and hit the power switch. I knew what the problem was from the first boot attempt due to trying to change drive letters in XP before I found out you cannot change the active partition letter (aka the one you currently boot to with Windows). I never knew how to revert the changes aside from reinstalling Windows. (Still don't.) What I don't know however is how in the world it managed to internally change the drive letter of the Vista installation when I was booted to my XP one. At this point I decided to install the OS Selector software, since the features looked promising. Shame that was a huge mistake. It allowed me to not even boot into any installed OS. While booting it went through things until it told me I didn't have enough disk space. While troubleshooting, I saw OSS somehow created two 4GB boot.ini files on my boot drive. After removing all but 1 OSS files (overlooked) I was forced to use the FIXMBR command in windows XP recovery console. After doing so I could boot back into my old XP install. This is where I halted things and came here to request whatever help I can get. Basically I want to know two things: 1) How did DD manage to internally change the drive letter of my Vista install? 2) Is there any way to revert this change without reinstalling Windows? I've spent a day mucking around and I'm very tired of doing this. I do not have the luxury to create image backups as I recently lost a hard drive due to mechanical failure and constantly burning to DVDs is very troublesome. I do not have any external hard drives either. With the way my drive is setup I'm not sure creating images will even work, nor have I even done so before. For reference: This is a 250GB drive with about 7% total free space across all partitions.