I bought a new Asus Windows 10 laptop with two hard drives on it. I used the windows disk tool to delete the whole volume that Windows is not on. The result is that all of the space on that drive was unallocated. (On a second attempt, I reformatted that drive and shrunk it so that only the NTFS data remained and the rest was unallocated, but that also didn't work.) I turned off fast startup in Windows power settings. I turned off Fast Boot and Secure boot in the Asus BIOS. I DLed Debian ISO and used Rufus to put it on my USB stick. The USB is booting in UEFI mode. When I boot from the stick, I use the graphical installer. When it eventually asks me where I want to install linux, it only gives me the option to install it on my 32Gb USB stick. I cannot get it to detect either of the two hard drives in the machine. How do I get it to do that?

silly question, but after all of the formatting and what not to the drives, have you looked inside the BIOS, are they still visible there?

If so, boot into the Live vs of the distro from your USB and look for them there. If not you can attempt to detect them via fdisk

Are you using Debian testing with the non-free firmware? Your new laptop will require a recent kernel.

Does the disk light come on at all? If so, you may be encountering a pitfall that I encountered - if the existing partition table is not usable, the Debian installer will report that there is no disk drive!

I solved this problem by zeroing out the partition table using Slackware's installer, and then creating a new partition table using Debian's installer. This works but loses the contents of the disk.
Ed

If there's an option to change the SATA controller from "raid" to "ahci" do so. Common issue with a lot of newer laptops, and will affect NVMe as well even though the setting is supposed to be SATA only.