I found this link. It apparently works for both Vista and Win 7. This is how to correct the "Bootmgr Missing" problem. Fixing "BOOTMGR is missing" Error While Trying to Boot Windows 7 or Vista - How-To Geek Read this and see if it helps.
Sadly, even trying to boot off the CD gives me the "BOOTMGR is missing" error, so I cannot repair the computer.
With the discussion continuiing about how you're unable to boot the Win7 installation CD from the CD drive, it might be a good time to point out that Win7 is installed from a DVD and requires a DVD drive to boot it to install.
The error you are receiving means the DVD is not booting regardless of the effort so far.
Follows these steps to correctly boot the DVD from a DVD drive: Boot from CD - How to Boot your Computer from a Bootable CD or DVD - Boot to CD
If you are not getting a prompt to "Press Any key to Boot DVD" then the boot order in BIOS setup is not set correctly with DVD drive in first position.
Try booting using the one-time BIOS Boot Menu key given on first boot screen: F8, ESC, or DEL on an Asus mobo.
Is it possible you have the Install DVD in a CD drive? This would explain why it won't boot and keeps bypassing OD to try booting HD.
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