Inspiron 7459 mSATA or M.2

Hello, I've got Dell Inspiron 7459 too and I've already bought new SSD instead of 32GB M.2 preinstalled, working as a cache for HDD drive. To be more specific I've put inside Transcend MTS400 256GB.
Here problems started showing up. First, I couldn't install new Windows 10 on the Transcend 256GB. Error 0x80300024 has been showing up every time I've been trying to install Windows from a bootable USB on a empty SSD that I've replaced. Than I tried to format system partition at HDD - didn't work too. After dozen of attempts I pulled out the HDD and than it finally worked - Windows 10 succesfully installed. Next I put my HDD back inside and now it's finally visible in the Windows tool responsible for viewing, changing and formating hard drives. 

What is my point. On the HDD I've got 3 partitions that I'm not sure what are they for. Could anyone expain me weather deleting it can cause any problems ? I'd like to have new clean Windows. I'd like to know if I can bring system back to the default configuration as Dell brought it to me when I purchased it and how to do that?

1. System partition EFI ( 500 MB )

2. Recovery partition (890 MB)

3. Recovery partition (14,30 GB)

And two more issues. After installing a new system on Transcend 256GB my right-screen sided controls responsible for display brightness adjusting do not react at all. How can I make it work again? I downloaded Dell Update assistant and it says that software is up to date. I have no idea how to solve it. I've already tried to change Windows registers like this (there's no effect though):

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000

FeatureTestControl = 0x0000ffff (65535)  (value before: 0x00008200)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0001

FeatureControl = 0x0000ffff (65535)  (value before 0x00000004)

The second one is that when i run my computer first I see is black screen for about 15 seconds, than Dell logo shows up for 8/10 seconds (with loading bar below and inscriptions in the right down corner what for are F2(bios) and F12(booting setup) - it has never been there before). After that Windows loads and it takes about 6/8 seconds which is good enough I think. Any ideas how to get rid off that black screen and loading bar below Dell's logo?

I'll be very greatful for any help! :)

Mine is M.2 32gb used for cache. It caused a bunch of problems so I ended up removing it completely and replaced the 5400 rpm data drive with a hybrid drive.

I do not want to Necro this thread but it might be good informations for whoever looking to upgrade the harddrive. I got a Transcend M.2 SSD 128Go (2242 size) and it work just fine. It's detected as a regular harddrive straight after install from the bios. This board does NOT support nvme drives but it does support regular M.2 drives with B+M notch. 

May i ask why the 32GB SSD is not shown up in the desktop since my purchase. 

also i want to upgrade the harddisk, what is the maximun capacity it will support. 

Many thx

Sorry but, how do you force  nvidia to be the main GC? Using Windows  I cannot obtain UHD resolution with  an external HDMI display and everything shows that it cannot be done (I've made an extensive search on Internet). BUT kubuntu can drive the display in UHD easily! (I have double boot) I have to do nothing but plug it and voila! If anyone have configured an external UHD display, I would appreciate your help.

Very useful information here!

Can someone help with the SATA connection here: Re: Looking for missing parts for SSD Inspiron 7459 - Dell Community

Thanks!