HOW TO install win81 on a store bought win 10 laptop, for dual booting?

[thesteelgeneral]

So yeah: how do I install windows 8.1 on a store bought lenovo g50-80 which already has windows 10, in order to dual boot both win81 and win10?
To be completely transparent the laptop does have a c:\windows.old folder which is about 18,100 MB or 18 gigs in size. This might be a win7 folder, i have no idea.


So. this is not going FROM windows 8.1 TO a dual boot with windows 10 but the REVERSE!

 

[GreyCatz]

So yeah: how do I install windows 8.1 on a store bought lenovo g50-80 which already has windows 10, in order to dual boot both win81 and win10?
To be completely transparent the laptop does have a c:\windows.old folder which is about 18,100 MB or 18 gigs in size. This might be a win7 folder, i have no idea.


So. this is not going FROM windows 8.1 TO a dual boot with windows 10 but the REVERSE!

Greetings, General!

I'm not sure I understand,
- you want to reverse or roll back a pre-installed Win10 licence to 8.1?
- and what other OS are you planning on using for dual boot?

Yours curiously,
GreyCatz.

 

[thesteelgeneral]

GreyCatz
i do NOT want to reverse or roll back a pre-installed Win10 licence to 8.1!!

I have Win10. I want to dual boot it with 8.1

 

[GreyCatz]

GreyCatz
i do NOT want to reverse or roll back a pre-installed Win10 licence to 8.1!!

I have Win10. I want to dual boot it with 8.1

Hello, General:

Well, it shouldn't be that difficult then.

1) Create and format a new volume on your existing disk and install your Win8.1 licence, or
2) Connect a second internal disk and install your Win8.1 licence on it .

Either way, when booting the Windows UEFI will prompt you to choose which OS you want to use.

Cheers,
GreyCatz.

 

[thesteelgeneral]

Sadly, when i tried that, it told me win81 doesnt install on GPT, even though i formatted it as NTFS with the windows 10 native tool Diskmgmt.msc.
Do you have ideas to get around that?

 

[GreyCatz]

Sadly, when i tried that, it told me win81 doesnt install on GPT, even though i formatted it as NTFS with the windows 10 native tool Diskmgmt.msc.
Do you have ideas to get around that?

Hello, General:

This is a bit unusual as Windows Setup requires a GPT disk to install. I can only suggest you try the CMD utility in Windows 10 and use the diskpart feature to re-format your drive as outlined by this guide:

http://www.neowin.net/news/guide-how-to-install-windows-10-from-a-usb-drive

The guide talks about installing Win10 from a USB drive, but your situation is basically the same.

If the format table doesn't indicate 'gpt', then after Step 6, type convert gpt and Enter, then move on to Step 7. Hopefully Windows Setup will recognize your drive as GPT in this case.

Cheers,
GreyCatz.

Update: If the problem persists, and the disk is in fact a GPT disk, then try to convert it to MBR by typing convert mbr instead.