If the system is set to RAID (IRST ON) mode, you need to pause the installation of Windows to insert the required Intel driver.  Alternatively, set the system setup (F2 at powerup) to RAID/IRST OFF and you won't need the driver.

See here:

https://www.intel.com/content/www/us/en/support/articles/000005864/technologies.html

For Linux, you will need a media set that includes support for both UEFI boot AND Intel RAID -- not a common thing to come with most released distributions; check with the support community for the distribution  you're trying to install.

Thanks for your help, but unfortunately, I'm prompted for the driver when RAID is on and when it's off. I've given up on installing Linux, but I still can't get Windows installed regardless of RAID being on.

So you can boot onto a USB drive to install UBUNTU....but not Windows?
The machine must be able to "One-Time-Boot" off a USB.
Are you using Dell's or Microsoft's "Create Bootable Media" process to make a bootable USB?

Welcome to the Dell Community @bswalsh 

Set everything to "Legacy" 

AHCI should be "Default"

Then try to install W10.

Your Alienware 17 R5 supports these operating systems:

https://www.dell.com/support/home/en-us/drivers/supportedos/alienware-17-r5?ref=oscompatibility

Best regards,

U2

I am assuming you mean you wiped the all Dell Factory Partitions on that drive too?
Both the Factory-Boot-Partition C: as well as the Factory-Image-Partition? It should still be Ok....
Dell's "Bootable Media" procedure worked well for me. Plus you get the factory image of Windows from Dell, with all relevant drivers included to create a bootable flash drive.
Also, I would, at this point, reset the BIOS to factory defaults.

The computer has a one terabyte spinning hard drive and a 256 GB SSD. I've used Gparted to wipe them both. I've done a factory reset on the BIOS, but doing so doesn't actually change any settings. Which is a bit curious. But I've done it by hand with the same results. I've tried RAID on and off, legacy options on and off, secure boot on and off, and various combinations. No luck.

As for Dell's bootable media, I only have Linux available to me (the broken laptop is my Windows machine) and the download options I've tried from Dell are Windows only. And I've had no luck running around them in WINE.

I've been using the downloadable .isos from the Windows official website. I've tried both 10 and 11 that way. I also found an older .iso for Windows 7 which I've used in the past, but that doesn't work here either.

I can boot the installation media on USB for both Windows and Linux. Windows will not install at all, when I hit the install button, it gives me the error I mentioned at the beginning of this thread.  Linux will install, or at least appear to, but it will not boot.

Thanks for trying, but I've already tried AHCI and all legacy, same results. I get that result with Windows 7, 10, and 11 (all the ones I've tried so far).

It was last working with raid on, and the configuration has you suggested. Upgraded to Windows 11. I guess I need to track down the drivers for those hard drives, love them to a different USB, and trying to install them during the windows install? But that still doesn't explain why I can't get Linux running. Which is really what I'd prefer.

Ok. So....the machine came with Windows10?
If the SSD/HDD combination is from the factory, then Raid should be turned off.
Raid-0 (2 drives striped) is useless anyway...total system loss, if either drive fails.
A mirror Raid set, or Raid-5 (3 drives) are the only valuable options.
So...it was last working with..... ?
ie) Windows10/SSD-boot-drive/HDD-data-drive...
Meaning, if it worked before, it should work again.
Even if you have to back-track drivers, etc.