Is Legacy/BIOS best when installing Win10? Or GPT/UEFI is best? 1

[javierdlm001]

I am about to create a dual boot with Win10 & Ubuntu.
I have a 2 months old desktop pc, Acer. So I was thinking of using GPT/UEFI for both, on the same SSD drive.
Is there any reason I should use Legacy/BIOS for Win10 instead?

 

[rclarke250]

nope.

 

[javierdlm001]

Thanks rclarke250

I'm getting an error. It says
"windows 10 cannot be installed. The partition is an EFI system partition."

Then to make things more confusing, I'm finding that everyone is advising that the solution is to switch the USB Drive with the Win10 installer from UEFI to Legacy!
I thought the idea was to keep everything either GPT/UEFI mode, or BIOS/LEGACY mode.
Should I switch the USB Drive then?

 

[javierdlm001]

So I decided to try. I switched the USB driver to Legacy.
But it didn't take me far.
It loaded this:
GRUB4DOS - then many numbers here
Windows NT6 Setup
1 Second part/continue NT6 Setup (boot first internal disk)

Then, it switched to a black screen with a blinking underscore.

So much for that!
What now?
Help!!!!! Lol

 

[rclarke250]

The first error means there is already a MBR partition on this disk, you would need to delete all existing partitions before creating the GPT disk. What USB drive?

 

[javierdlm001]

Finally got Win10 installed!

I had a small 200 Mb partition with Fat32/Primary and a boot/ESP flag,
200 Mb of unallocated space,
and the rest for NTFS/Primary.
It worked! No complaints this time!
The difference is that before I had only 2 partitions:
1. NTFS with a boot/ESP flag (for Win10), and
2. Ext4 (for Ubuntu).
So I didn't have the small Fat32 partition for the booting files, but also I didn't have a small unallocated space available for the Windows installer.

I have updated Windows Defender and it's doing a quick scan.
Next I'll start File History.
I'll use it for a couple days to ensure everything is running ok.
Then next time I have a chance I'll install Ubuntu too, in about a week. Should this linger, I'll just wait for 16.10 to be released next month.
Also, I still have to re-plug the HDD with Ubuntu Studio. I imagine I'll have to do some GRUB fixing, I hope not.

Thank you so much for your help rclarke250