Insider Preview Trouble dual booting Windows 10 with 8.1


Active Member
I have a Sony Vaio Fit laptop. It is my main working (and only btw :p) laptop. So I thought I'd just dual boot Windows 10 with 8.1. So, I created a 40GB partition on my hard drive. I downloaded the x64 version of Windows 10 and burned it to a USB drive with Windows 7 DVD USB tool installer. I changed the BIOS settings such as boot from external drive 'enabled' and put that option on top of the list. Disabled the secure boot as well. And when I select boot from USB option, it says booting from external device failed, that is when the boot mode is selected as UEFI in BIOS settings. When I change it to Legacy mode, I'm able to get past the Install now screen and the choose upgrade or custom installation. But when I choose custom installation, and I'm allowed to choose a drive on which I want to install the preview and when I select the drive I have created, it says, Windows can't be installed because the selected disk is of GPT partition type, or something like this. What am I doing wrong? Please, someone help me out. Thanks.


Excellent Member
Microsoft Community Contributor
Bassfisher is correct, the Windows tool, at least in the past, would format the USB drive as NTFS which will not work with UEFI.

However, I don't use Rufus, but it might be easier if you are not acquainted with using Diskpart in the Command Prompt window.

You do have backups for your current system, since things can go wrong and you may loose your current install..


Noob Whisperer
I agree Rufus will do the trick.



Windows Forum Team
Staff member
Premium Supporter
I agree that rufus will do what you asked (the 7 tool is only for 7) but it is a very bad idea to dual windows X with your only working system--- X is a demo and will have bugs!

8.1 can run hyper-v or vmware player (both can be used as free) to v-boot windows x and is much safer than what you are doing but yes--- it's your machine so good luck.


Essential Member
Premium Supporter
Perhaps there could be a cross function that could interfere with a dual boot system, but I cannot honestly say where that could possibly occur.. I have three dual boots running at the moment, between Windows 7 and Windows 10 in one instance, Windows 8.1 and Windows 10 in the others.
Only real problem is possible complications with the Boot menu. These can always be adjusted when the systems are up and running.
I have no real wish to use UEFI or the secure boot found in the more modern Computers. I had one Laptop, with the similar characteristics to that described in the op. I removed the secure boot option also, in the bios, formatted the drive and went ahead, without incident, with the installation. But, the bad news there is that if you have factory re installs etc, in hidden partitions, it will destroy them all. I keep constant images so, in my case, it was not a consideration.


Active Member
Thanks guys. Finally it worked with Rufus. So far, I didn't face any problem after dual booting. And by the way, I have backup of all my data so I don't mind if something went awry. Thanks so much for the help.


Dave is right... there is no potential harm w/ dual boot.

All the Beta Testing I / we did for & w/ Microsoft through all the Builds for Vista, Windows 7 & Windows 8 were done using dual, even triple boot, VMs or spare boxes. Ten is no different. The 3 ideal or best ways for using Beta OS Previews are multi boot, VMs or on non-production (spare) boxes..



Essential Member
I'm running a triple 7 Home premium, 8.1 Pro and Windows 10 Tech Preview. Not ever had a problem dual booting or triple booting...although I would prefer to dual/triple boot off separate HDD's....but since is my only PC at the moment, laptop, I'm forced to dual/triple boot off a single HDD.