Hi @Doc416 ,

Check out this benchmark result submitted by a 990 user. It shows Samsung 850 Evo 1TB SSD running as Win10 OS drive with no problem. It should be fine on yours as well.

OptiPlex 990, as well as Win10 OS, support both Legacy BIOS and UEFI boot. However, if you choose boot with Legacy BIOS, format your drive as MBR allocation table format; or if you choose UEFI, format hard drive as GPT.

For SATA operation options, suppose you don't have legacy IDE device and no need setup RAID, choose AHCI then.

MBR Legacy booting is not permitted with NTFS and windows 10.

You cannot MBR Fat32 boot windows.

Newer Versions of Bios will require Secure Boot Off and Legacy Option Roms enabled on and UEFI/GPT booting with the 4 partition structure instead of the 2 partition version that windows 7 used.

https://www.7-zip.org/download.html

There will be system,  MSR,  Recovery,  OS   instead of   MSR and OS.

Absolutely works fine but I recommend installing 7zip and then downloading the windows 7 CAB file for the 990

https://downloads.dell.com/FOLDER02161719M/1/990-win7-A10-5GWVN.CAB

You save to the mydocuments folder and then right click with 7zip and extract to that folder.

Then go thru device manager and update the drivers from my PC instead of the internet for all of the yellow !

Do this also for the audio codecs and intel graphics.

There will be many updates after that even if you start with 1809.

Windows 10 is not officially supported but it works fine.

I have started recommending users buy at least 1 copy of 1809 on system builder DVD so that they can re install any Dell from 2006 all the way thru 2019.

I use an external Powered USB DVD/Blueray drive and F12 boot from the DVD and select UEFI boot and install clean.

This works for all my dells from 2006 Optiplex GX620 thru my new Made in Jan 22, 2019 G7 Laptop that I purchased at Best Buy a few days ago.

Not supported DOES NOT mean not working.

Curious what BIOS setting you used for Windows 10 on Optiplex 990?  I can not find Secure Boot in my 990 BIOS.

Secure boot requires UEFI Class 2.3.1 bios.  990 does not and will never have this. There are no WIN10 drivers for the 990. There are Windows 7 cab files that can be saved into the my documents folder then contents extracted using 7 zip.  That way you can right click on any yellow !  in device manager and say update from my machine instead of from the internet.  Secure boot does not allow 32 bit os or XP etc.  The 990 can boot 32 bit xp because it has class 1 bios.

https://downloads.dell.com/FOLDER02161719M/1/990-win7-A10-5GWVN.CAB

https://www.7-zip.org/download.html

You must set sata operation to AHCI and install win10 using windows 10 dvd.

If you have dell oem WIN7 coa you can use that to activate windows after install.

https://www.newegg.com/microsoft-windows-10-pro-64-bit-reinstall-recovery-disc-only-no-license-key-included/p/N82E16832350238

What about spectre and meltdown?

I guess you meant w10, 64bit V1909 right using the MS stick builder,  ? ISO tool from MS ,right

I will assume you meant 64bit, 32bit is DEAD forget it ever exited, ok? and the 64bit kernel is super secure..

2011 PC, 9 years old. Intel Gen2 Sandy Bridge Core i3, i5, i7,,  Q67 chipset, and will run w10 for sure.32bit at least..

ACHI  is the answer, (slam dunk never use RST period) ask. use MS RAID arrays only, or PRO CLASS choices if doing RAID Im sure your not doing RAID RIGHT? only you know that.

there is no Intel RST  w10 support for this old PC, it ended. at old series 100 not series 6 you.

next is and emotional issues (fear, FUD and security, endlessly and non ending ) UEFI Class 2 here..

only you know if you want UEFI,  secure  boot is the word,  (TPM never)

IS BIOS fresh and newest version be best for sure, use F12 key BIOS UPgrade if seen there, if not ask...

set the PC to legacy  ( UEFI can work but GPU cards can be a pain IN THIS MODE)

the OS costs nothing to try,  just do it.  per above. choices. mostly all those are yours alone

No RST turn that monster off..

ACHI

legacy

safe boot off (many not be seen there), if seen, TPM off

PEX off

set boot order correct.

done.

Try to know I have have never run all versions of every BIOS made and uses by dell, only newest,

what old versions do , IDK ,nor CARE.

The PC has CPU.. not posting what CPU you have using real intel names, makes answers super hard.

did you know many PCs this old are sold as used and downgraded to LAME CELERONs.  yah,  problematic that..

But no worry, the MS installer will tell you that, NOT SUPPORTED this PC, (wrong CPU tops list)

nobody I know tested all Gen2 CPU made any PC, not yet. like the junky G440 CPU,?

SOME refurb shops sell the I5 CPU on fleabay , put in a $2 Cerary chip and sell the PC, endless examples.

so what CPU do you have, I can not guess, CPU..

well lets say you did install w10 64bit v1909

what might fail..

The only failurers I see, are:

IGPU not working.. at full spec and resolution , gen 2 I7 is.  Intel® HD Graphics 2000 ,(zero)

and is not fully supported by Dell, nor Intel nor MS,  w10 loads limphome HD2000 driver there, and screen works but is crippled,  so put in any series 7 up GTX card you wan;t problems cured.

the Q67 is supported, (not RST)but all else is.. this is the south bridge chip, a key part..

my 790 runs w10-64, perfectly even in UEFI boot mode. yeah it does... with$10 gpu card fully (ask)

connect the Ethernet port to your router

load 10-64 and it will load, then check DM disk manger see all chips working SEE? and iGPU in cripple mode

newer GPU and bingo, no need to force w7 drivers in to w10 why that,?

load the thing and address problems you see,, brave up  do it , there is no cost for w10 why be so shy, seen vast times here, like the installer will catch the PC on fire, wow thinks this?

the only questions are.  AHCI (RST is dead) and legacy load W10 64 bit in BIOS legacy mode. IT WILL do all the formatting for you no cries of MBR or anything at all like that, why do folks make this so hard> IDK.

if Realtek ALC269 High Definition Audio Driver  sound/audio fails, try this at dell.com

the only thing with sound is some folks demand fancy sound managers,  so not me.  if it can play Lui-Lui me happy.

what stops you? IDK

load it

run it

see what you dont ;like and post that, post something real, no really.

The HD2000 you may not like but iff all you do is read email and post here, you be happy.

gaming never. Intel ended this, not dell, intel is blame, and for RST , x10 more blame.. ended far sooner .

ended  for before series 100 south bridges.

if any chip can not be made to work there are 2 cures, compatibility mode w8 for sure up and  add a new card.. or dongle cures, endless and dirt cheap.

I just installed a SSD into my optiplex 990 & was having issues installing all versions windows from xp to windows 10 home from disk ,so i downloaded windows 10 onto a usb drive. windows 10 home wont install but windows pro does without issue, not sure why!

Intel has already said that it wont patch some older processors.

Oldest unit addressed is the 9010 7010 3010

You can test for it

https://www.dell.com/support/kbdoc/en-us/000177783/

https://www.grc.com/inspectre.htm