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I have Windows XP installed on one drive, and have just installed Windows 7 on another.

I can boot into either thanks to the boot menu. However, if I unplug the XP drive, Windows 7 fails to boot. The boot menu is installed on the first drive.

The same happens if I use the bios to select the Windows 7 disk as the startup disk. I get BOOTMGR missing. I'd like to remove the old disk soon, since it won't be needed, and replace it with a larger one for storage.

When I boot into Windows 7, and run the bcdedit command line tool, it shows that the bootmgr is on d: and windows is on c:.

So, how can I install the bootmgr on the drive with Windows 7 on it?

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Saying Windows A is on C: and Windows B is on D:. is entirely useless, note. Separate versions of Windows on the same machine can each have their own drive letters, and drive letterings are meaningless as descriptions of where the partitions are. Microsoft provides a diskpart tool, with list volume and list partition commands, for providing exactly this sort of information in situations like this without the confusion of drive letters. It wasn't necessary in this case, but always use the output of diskpart to show a hard disc layout in future, not meaningless drive letters. –  JdeBP Jul 7 '11 at 14:15
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Well within the context of running Windows 7 that's EXACTLY what it says. If I paraphrase, let me say that Windows XP is on Drive #1 and Windows 7 is on Drive #2. There is a boot menu on Drive #1 (with xp) which lets me choose. Why on earth does Windows 7 not install a boot manager on disk #2?? –  Matt Connolly Jul 7 '11 at 23:34

2 Answers 2

up vote 2 down vote accepted

I tried a program called EasyBCD. There's an option in there for change boot disk, which sets up everything that is required on the second disk. Now I can select the boot disk from the BIOS and boot that disk, which means I'm free to remove other disks without loosing my operating system. The guy who wrote that should be paid big $$ by microsoft for picking up their slack.

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You've already done what this SuperUser questioner is intending to do, and are hitting the problem that xe is worrying about.

The answer is the same.

You've got a combined boot+system volume. This is a poor idea, and something that even the x86 PC world has finally moved away from in the years since Windows XP was released. Windows 7 when installed on an empty system will create separate boot and system volumes.

You currently have your system volume, combined into the Windows XP boot volume, on your first hard disc. As you've discovered, if you remove the system volume (or format it, or make the partition inaccessible in some way), you will indeed render your system unbootable. It is not just a Windows XP boot volume that can be re-formatted or thrown away. It is your system volume as well; and is, as the name says, an essential part of the system.

As you've also discovered, your Windows 7 boot volume isn't directly bootable. It is your system volume that must be bootstrapped by your PC/AT firmware. (This has in fact always been the case for Windows NT. It's simply that before Windows 7 only on non-x86 versions of Windows NT was separate boot and system volumes the norm for installing the operating system. It's now the norm for everyone.)

What you need is a separate system volume, moved on to your second hard disc. What you should not do is have another combined boot+system volume on your second hard disc, because you'll just store up for yourself the very same problem that you are having now, all over again further down the road. Keep the system volume separate from your boot volume(s). It only contains a few things, and you shouldn't need to touch it in normal operation, even for a complete reinstall of Windows 7.

Microsoft provides a lengthy procedure for doing exactly what you want to do. You simply need to use your favourite partition management utility to move things around on your second hard disc, and re-size partitions, to make enough room for a 200MiB NTFS partition at the start of that disc. Then follow Microsoft's procedure.

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