Windows 10: Windows 10 PC crashed won't restart C: and D: drives appear to have switched

Windows 10 PC crashed and won't restart. The C: and D: drives appear to have switched.

Won't even start in Safe Mode

Can get to command prompt, and when I dir, it seems that everything that should be on the C: drive is showing as being on the D: drive, and vice versa.

None of the other options from the fix menus work, not even re-installing Wndows / reset PC

PC is a gaming machine, about 8 months old. Still under warranty but computer shop is closed due to Covid-19 :-

Can anyone suggest a fix, please?

:)

 

Switching C: and D: drives

Summary: In my file explorer, two drives appear. My C drive, where my Windows 10 OS is installed, and my D drive. My C drive is 476 (500) GB, my D drive is 1.8 (2) TB. I would like to switch my C and D drives so the 2TB hard drive is my default, where my
OS is installed, etc. My C drive currently has 290 GB used and 186 unused.

Notes: The D drive does not appear under Settings/Storage - only my C drive appears here. Both drives appear in the Task Manager, labelled "Disk 0 (C" and "Disk 1 (D" which leads me to believe these are physically separate disks, not
partitions - but I could be wrong, please clarify this. To be clear, I cannot see any data stored on my D: drive. Though Task Manager/Performance/Disk 1 says "Formatted: 1.8 TB", when you select the D: drive in File Explorer it states the drive is not
formatted and must be formatted before it can be accessed, then asks if I would like to format the disk (I have not done so). I am willing to reset my computer; all of my files are saved to the cloud and I am in the process of creating a USB recovery drive
as I type this.

Questions: Is this possible? Is this worthwhile? If both possible and worthwhile, how do I do it?

Specifications:

1. This is an ASUS Q530U laptop (not to be confused with the Q530UX or Q530UZ). That is the sticker on the outside of the laptop. Inside the Settings/About it says "Q534UXK". I am not entirely sure why this discrepancy exists but I would trust the sticker
first.

2. Intel core processor: i7-7500U CPU @ 2.70 GHz 2.90 GHz with 2 cores and 4 logical processors. (not overclocked manually but I often see it running between 3.0-3.4 GHz) Also noteworthy is that in the Task Manager, the system recognizes it to have a base
speed of 2.90 GHz. I am not sure why the 2.70 GHz is included in the name of the processor but nobody truly understands Intel's naming system, so.

3. 16.0 GB RAM, 15.9 usable, 2133 MHz

4. Two graphics cards on board, the Intel(R) HD Graphics 620 and NVIDIA GeForce GTX950M

5. See summary for drive information

 

CMD won't switch from c: to d:

My dad's Dell Optiplex 9010 has Windows 10 as his operating system. He said it was acting weird so he restarted it. When it rebooted, it came up with the error message bad_system_config_info. It then restarts, tries to repair itself, then brings up the options to restart or advanced options. I looked up a YouTube video (because I know nothing about software) and he goes into the command prompt, and switches from c: to d:. When I try to do the same, it says "The device is not ready." Like I've said, I have no idea what I'm doing. I read that it's because the CD drive isn't active. I tried putting a random CD in but it didn't work. Can someone please explain what I'm doing wrong!
EDITED TO ADD: My dad bought a USB drive by EZALINK with windows 10 loaded on it, but it can also be used to boot the system so we can access the internet.
EDITED TO ADD: I tried the CD prompt listed in the comments, but it still says "The device is not ready". Please dont get this question closed by saying it's a duplicate. All the command prompts that have been suggested are not working.

 

My C: Drive does not appear in Explorer - Windows 10

Suddenly my C: drive does not appear in Windows Explorer. My SSD (E: ) and my DVD (D: ) do appear.
The computer works fine in all other respects.
Windows 10, Fall Creators Update.

Any suggestions?

Thanks,