Hello everyone,
I just spent a few hours with this and figured I'd let the world know of yet another silly installer issue with Microsoft Windows.
While installing Windows 7, there will be a list of hard drives that you can install to. If there is ANY drive higher on the list than your intended install drive, Windows 7 will install the BOOTMGR to that drive instead of the drive you installed to. This makes for an interesting problem. After the installation has finished, when you select your installed drive as the boot device, you get "BOOTMGR is missing" error. Then, when you select the drive that was higher on the list as your boot device, you get Windows 7 booting up FROM THE OTHER INSTALLED DISK.
Solution: While installing, if there is any disk higher on the list than your intended install disk, shutdown, disconnect the drive, and restart into the Windows 7 installation. Make sure your intended installation disk is the top drive on the list. That will get you past this on the install.
NOTE: After the first strange install, I tried running the bootrec /fixboot, bootrec, fixmbr, bootrec /rebuildbcd and none of them worked, so I suspect there's something more behind the scenes that I'm missing. However, I am not interested in a study of how it all works right now, so I'm doing the reinstall.
...reminds me of the Windows XP installer arbitrarily calling a flash card reader C: and installing to F: making for a beautiful F:\WINDOWS installation.
Best,
Cristobal