Solved Win 7 & 8 manually add dual boot.

I had Win7, removed the HD, and installed Win8 on a new HD.

NOW, I want to make the Win8 drive dual bootable.

I want to use the built in boot menu...

http://www.eightforums.com/tutorials/2344-dual-boot-installation-windows-8-windows-7-vista.html

or use if both are installed.
EasyBCD - NeoSmart Technologies

If your ASUS has a UEFI/BIOS firmware, both OS's will need to be installed in the same mode. (UEFI or Legacy)

No need to use any software to setup dual boot.

From Windows 8. Open the elevated command prompt and type:

bcdboot X:\windows =====> where X is the drive letter of the Windows 7

The command to add another OS to a boot menu is Bootrec /RebuildBCD which must be run from the Windows Recovery Environment to get access to the utility. EasyBCD, as Theog suggests, is an alternative.

If you have a preference as to one drive being the surviving install, you might make sure it is set as primary in the bios. And I am assuming you have a Legacy (MBR) install.

Or you can use the Boot Menu key to select the OS during boot, since you have two independent installs.

Sorry, I even gave you the wrong command. The /Scanos flag just looks for an install. The /RebuildBCD flag gives you the opportunity to add the install to the boot menu.

I have corrected the original post.

Bootrec /Scanos says only 1 OS is found. I have yet to try /RebuildBCD, but I have the feeling it's not going to work.

Advice on what to does?

Did you try EasyBCD?

I did. I had to re-install Windows 8.

JoesMorgue said:

I had Win7, removed the HD, and installed Win8 on a new HD.

NOW, I want to make the Win8 drive dual bootable.

I want to use the built in boot menu...

Click to expand...

just to clarify ,you put the win7 drive back in the computer correct ,or do you want to partition the win8 drive and install win7 on that partition

I removed the HD with with 7 and a second HD, installed Win 8 on a third, put the 1st and second HDs back in.

I do find it weird, while in Win8, and exploring the Win7 OS, I can go into folders that other windows OSs keep me locked out of.

JoesMorgue said:

Bootrec /Scanos says only 1 OS is found. I have yet to try /RebuildBCD, but I have the feeling it's not going to work.

Advice on what to does?

Click to expand...

The command finds installs that are not yet included in the boot menu. If it says it is finding 1 OS, then it is not the one you already have an option to boot.