new computer won't boot from old SSD

[StenyH]

I got a new computer, an alienware x51. Turns out I hate Windows 8, so I installed my old computer's harddrive, which is an Intel SSD with Windows 7 on it. When I boot from the Windows 8 HDD, I can access the SSD. But when I unplug the Windows 8 HDD, it won't boot from the SSD.

Could someone please tell me what I need to do so that it boots from the SSD into Windows 7?

Thanks!!

 

[Bubbaleone]

Before you installed Windows 8 on it, if that HDD (or any other drive) was in your old computer and connected along with the SSD, when you installed Windows 7 on the SSD the Windows 7 boot configuration data was probably written to the second drive.

It's well documented that the Windows 7 Installer will write the boot configuration data to the second drive when two drives are connected, rather than writing the boot configuration data to the drive Windows 7 is actually installed on.

I'd suggest you follow these instructions: How To Rebuild the BCD in Windows


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[StenyH]

The windows 7 disc boots in my old computer fine, even when it's the only hard drive plugged in. It won't boot on the new Alienware X51.

 

[Bubbaleone]

Then you'll need to determine whether you installed Windows 7 in AHCI or IDE mode on your old computer. If, for example, you installed Windows 7 in IDE mode on the old computer and the X51 is currently in AHCI mode the SSD won't boot. If that's the case, the fix is fairly simple but check that first and then post back with your findings.

 

[postmortemIA]

it is very unlikely that installation from a different PC will run just fine on yours.

 

[Bubbaleone]

I just looked at the specs on the X51; being a Dell and having Windows 8 preinstalled also means that secure boot is enabled in UEFI. Before you'll even be able to determine (as noted by postmortemIA) whether the SSD will boot to the new hardware, you'll need to disable the secure boot feature.

 

[StenyH]

Then you'll need to determine whether you installed Windows 7 in AHCI or IDE mode on your old computer. If, for example, you installed Windows 7 in IDE mode on the old computer and the X51 is currently in AHCI mode the SSD won't boot. If that's the case, the fix is fairly simple but check that first and then post back with your findings.

Thanks, how do I check?

I disabled secure boot.

 

[Bubbaleone]

Connect the SSD back into the old computer, boot into Windows, then follow these instructions;

• Open regedit.
• Go to: HKEY_LOCAL_MACHINE\System\CurrentControlSet\services\msahci
• Click on msahci, then in the right pane double-click the value Start.
• Change the value data to 0, then click OK.
• Close regedit, then shutdown the computer.
• Remove the SSD from the old PC and connect it into the X51

This registry edit will ensure that with the X51 in AHCI mode, Windows 7 will now be enabled to boot in AHCI mode (if it's going to boot at all).

To check whether the Windows 7 installation on the SSD will actually boot you'll need to disconnect the X51's HDD, and disconnect any external or flash drives as well. In BIOS; check that AHCI mode is enabled, that the SSD is correctly identified, and that the SSD is set first in the boot order. It's possible that it may boot to Windows but more likely you'll receive an error message. Try it, note any error messages, then post back with the results.


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