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J G

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UEFI VS Legacy questions

I have a dell inspiron 7000, with a 500g SSD, Win 10 pro.  As far as I can tell, the laptop came configured with WIN 10 installed and BIOS mode set to Legacy mode. When I plug in USB DVD to boot from, when I hit f12/select boot options, the USB DVD/CD drive shows up as a generic DVD/CD under legacy, but then shows up as the only option in UEFI as ASUS DVD/CD drive.  I am able to boot from the DVD under the UEFI option, but not the Legacy.

My questions are:  
1) It seems like both legacy and uefi are concurrently running, is that possible?
2) I assume since the laptop came pre-configured like this that it is a correct configuration?
3) If I want to replace the SSD, should I just leave the bios settings the same?
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John
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1. No. It is one or the other. It is likely a UEFI system. Any Windows 10 system I know of that came out in the last 2 years or so, would be UEFI.

2. If the laptop came UEFI, that is the correct way.

3. If UEFI, leave the BIOS settings the same if you wish to change the SSD.
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J G

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When I go into the BIOS, UEFI is not selected.  Legacy mode is.  I'm just trying to make sense of this.  Is it in a hybridized mode of some sort?  

How can I absoloutely tell which mode it is in?
I have not seen that before.

Set BIOS to UEFI, then update it (if an update is available), restart and see if UEFI remains set.

There is no reason any more to use legacy BIOS
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arnold
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can you post a picture  showing the uefi / legacy settings?
"If it ain't broke, don't fix it" is always good advice.

You should be aware that UEFI and Legacy BIOS are terms that apply to more than one thing:
Legacy is a key word here - more so than BIOS I would say.

UEFI is just a new name for BIOS but it does carry some new features which are important.
UEFI is also a characteristic of boot media and this is where "Legacy" vs. "UEFI" comes in.
Most computers can boot from both and, as you are seeing, the media devices can show up twice in order to treat them one way or the other.
Then there is Safe Boot built into UEFI BIOSes which affects your ability to boot from various media.  It's more convenient for Safe Boot to be turned off.  I don't think this affects the ability to boot if changed from Enabled to Disabled.  But it well may if changed from Disabled to Enabled (for some media).
Then there is the drive type: MBR or GPT.  GPT is what allows greater than 2TB and is probably not available using Legacy tools.  But, I'm reluctant to tie these things together necessarily.  That's why I mention it here.
UEFI is just a new name for BIOS

Not really. UEFI can do pre-boot stuff that BIOS cannot even touch. BIOS will be gone in a year or so.

So use UEFI if it is available.
It depends on what you mean by "BIOS" in the first place.  
To me, it's an entity that provides pre-boot capabilities and some device controls.
Using that definition, the UEFI is just another such entity that does these same things .. and more and in different ways.

But, if you're hung up on making them "different" things in context then read this which carries that terminology along:
https://www.maketecheasier.com/differences-between-uefi-and-bios/

The entire launch of UEFI was awkward to say the least and much useless discussion ensues because of that.
The inclusion of *restrictive* security functionality was amongst those things that made the transition harder (e.g. Safe Boot).
BIOS from before time began to now can start a PC and do some settings.

UEFI can run programs with some limited graphical interfaces. Old BIOS cannot do this.
As I said earlier, UEFI does more things and does some things differently.
It appears that John confirms this.