Install Windows 10 as dual boot without USB or DVD

Hi guys,

I have the Windows 10 Pro ISO with a Windows 10 key. (from MSDN)

I want to install Windows 10 as dual boot with Windows 8.1. Both are x64.

Is it possible to install Windows 10 from the ISO? I know you can upgrade that way. But I want to do a clean install AND install alongside Windows 8.1.

nushydude said:

Hi guys,

I have the Windows 10 Pro ISO with a Windows 10 key. (from MSDN)

I want to install Windows 10 as dual boot with Windows 8.1. Both are x64.

Is it possible to install Windows 10 from the ISO? I know you can upgrade that way. But I want to do a clean install AND install alongside Windows 8.1.

Create a new partition on your drive or install to a separate drive, should have no problems.

Bazz said:

Create a new partition on your drive or install to a separate drive, should have no problems.

I have cleared a partition for Windows 10.
C:\ = primary = 100GB: has Windows 8.1 on it
D:\ = primary = to be used for Windows 10
E:\ = logical/secondary = data partition

There are other system partitions too.

So you are saying that I can simply mount the ISO in Windows 8.1 and run the setup and choose D: partition as the install location for Windows 10 and it will work?

I tried it. Sadly, the installer doesn't give the option to choose the partition. It just uses the same partition where Windows 8.1 is installed.

I only get 3 options.

1. Save settings and user data : means, upgrade
2. Save only user data : means, upgrade
3. Delete everything : means clean installation deleting windows 8.1

Does the installer give you the option to perform a custom install? Akin to the following page:
How to Dual-Boot Windows 10 with Windows 7 or 8

Without researching, the fastest answer I can give you would be the following.

1) Disconnect your existing HDD.
2) Connect a new/spare HDD.
3) Install Windows 10 to the new/spare.
4) Reconnect previous HDD.
5) Ghost/Clone the new/spare to your partition on the previous HDD.
6) Run the Windows boot repair on Windows 8 or 10, they should both add the second entry. (Or manually add the entry using Bootcfg?)

Shamalanana said:

Without researching, the fastest answer I can give you would be the following.

1) Disconnect your existing HDD.
2) Connect a new/spare HDD.
3) Install Windows 10 to the new/spare.
4) Reconnect previous HDD.
5) Ghost/Clone the new/spare to your partition on the previous HDD.
6) Run the Windows boot repair on Windows 8 or 10, they should both add the second entry. (Or manually add the entry using Bootcfg?)

Too tedious. I'll probably get someone burn a DVD then.

i downloaded Windows 10 in VHD format. Can it be used to install Windows? For example, copy everything on it to the physical partition, do a boot repair and Windows will make it bootable? After that, it will probably redetect all the hardware?

Williams said:

How windows RTM related with your problem. ?

Because that guide is from last year so it refers to preview builds.

Microsoft probably removed the ability to mount a Windows 10 RTM ISO and run the setup from there to install it as dual boot. I have no other explanation why the custom install option isn't showing. This probably is due to activation.