Found it, lol. Now which scheme to choose? Is there anything else I need to know about this feature, if so any link? Thanks.
Well, you'll see that, with Alt-E, "MBR for BIOS or UEFI/CSM" gets replaced with "MBR for BIOS or UEFI" (notice that "CSM" was dropped), which means dual BIOS and UEFI boot. So that's the scheme to choose.
Well I toggle between modes (disable dual uefi/bios mode) and CSM never comes back even if I restart the program...
No. As any technician should know GPT is incompatible with booting from BIOS. The GPT partition scheme was conceived alongside UEFI, precisely as a means to work around the limitations of the MBR partition scheme. GPT does away with the one key element that allows a BIOS system to boot an HDD or an UFD (which is also what gave its name to the partition scheme): the Master Boot Record. The Master Boot Record is executable code, residing in the very first sector of a disk, that a BIOS system actively looks for to determine if a system is a bootable. The very last step a BIOS firmware will perform is to hand over execution to this MBR code to allow boot. Therefore, if you have a GPT disk, there's no MBR code to boot from, and thus your disk can only be booted from UEFI, not BIOS.
Yes I already know this. What I meant to say is if Rufus is capable of a boot like a install DVD which already has both scenarios UEFI/BIOS and GPT/MBR combinations.
Using 2.6 already cause I overwrote previous version and launching it from a shortcut on Windows 8.1. When toggling modes Rufus says the mode is enabled or disabled and it keeps that way even when closing and opening once again. The problem is in the scheme mode where CSM never comes back again...
Outside of oddities like protective MBR, there's NO SUCH thing as GPT+MBR, especially for (non ISOHybrid) optical discs, as they don't use either. At least for BIOS, and for historical reasons, optical discs generally use a different boot process from HDDs/UFDs, which is actually why converting an ISO to USB can be very tricky. Anything that's dual BIOS+UEFI is necessarily MBR. Recent Windows ISOs are dual BIOS+UEFI. But there's nothing GPT about them. So, again, you should always use MBR, never GPT, if your aim is to create an HDD or UFD that is dual BIOS+UEFI bootable. And to answer your auestion, yes, the whole point of Alt-E in Rufus is to enable dual BIOS+UEFI as the Windows ISOs. Please make sure you have a dual BIOS+UEFI Windows ISO selected (preferably Windows 8 or later). Alt-E only applies to Windows ISOs, and if you have such an ISO selected. I see no issue whatsoever with Rufus 2.6 when using a Windows 10 ISO, i.e. the "CSM" part appears and disappears as expected according to whether dual BIOS+UEFI is enabled or disabled. Which Windows ISO have you been using?
I wasn't using any iso. As soon as I selected one CSM came back. I was playing with Alt+E right when you told me about Dual BIOS+UEFI feature without using an iso. So now everything is fine. Thank you for elaborating the dual boot thing.