Windows Defender Offline scan won't work

If the Windows test fails I'd Test the RAM overnight to stress it with the best bootable test memtest86, following this guide to test both sticks and slots:

https://www.tomshardware.com/how-to/how-to-test...

The Crucial scan is only to get the definitive specs of your RAM, how it's configured and how much more it can take. They also offer first quality discount RAM.

Those articles are what I found that others with this problem have tried. But if you have the latest version and already did a Repair Upgrade then you can skip those. Likewise if you've already done those malware scans and SFC with DISM then you can skip that.

You mentioned 100% disk usage which is also a known issue with fixes here:

1. See fixes here for 100% disk usage:

https://www.cleverfiles.com/howto/100-disk-usag...

https://www.makeuseof.com/tips-fix-100-disk-usa...

https://www.technology.org/2019/07/07/how-to-fi...

http://www.thewindowsclub.com/fix-100-disk-usag...

https://www.kapilarya.com/fix-windows-10-100-pe...

2. Update your drivers from the PC or motherboard maker's Support Downloads web page, using the full model number, Serial Number or Dell Service Tag on sticker. Compare the latest drivers available for download with the ones presently installed in Device Manager reached by right clicking the Start Menu. Make sure you have the latest BIOS or UEFI firmware, Chipset, Display (Video), Sound, USB3, Bluetooth, Network and all other drivers, or else download and install the latest now.
3. Go over this checklist to make sure the install is set up correctly, optimized for best performance, and any needed repairs get done: http://answers.microsoft.com/en-us/windows/wiki...

Start with Step 4 to turn off Startup freeloaders which can conflict and cause issues, then Step 7 to check for infection the most thorough way, then step 10 to check for damaged System Files, and also Step 16 to test a new Local Admin account. Then continue with the other steps to go over your install most thoroughly.

Keep me posted on your progress as I will be here to help until the case is resolved.

Okay thanks for the tip about readyboost. 

Usually from what I can remember when I check Task Manager what's slowing down the computer in the HDD rather than the RAM or CPU. The HDD is usually at 100% when the other two are maybe at 50% or so. As for the RAM...I haven't had an issue since that one time the laptop crashed but when that happened I ran Windows Memory Diagnostic and the RAM failed the test. But I haven't had an issue since. Can that cause the problems I am experiencing or is that not plausible? Is it still necessary to run the crucial scan if the RAM already failed the windows diagnostic? 

Also I don't mean to be dense but I'm not sure what you want me to do with the articles you sent. The one talked about doing the repair upgrade again and about updates, right? And the second article is about a defender update in 2020 but I think the laptop is up to date currently so is that still an issue?

Should I continue to think it might be malware or virus after all of the scans I've run?

Looks correct, tho I'd not use Readyboost but instead optimize your paging file:

https://www.online-tech-tips.com/computer-tips/...

Then if observing your CPU vs. Memory under load in Task Manager shows the Memory being used a lot more than CPU or getting close to max usage under load, then I'd Run Crucial System Scanner to check the RAM is properly spec'd and configured, what upgrade options exist for first quality RAM: https://www.crucial.com/usa/en/systemscanner?cm...

Let me know the results of any steps I gave that you've not reported back on yet, including in the articles or tutorials I gave.

I hope the pic I posted is alright. I don't have the computer connected to the internet right now in case it's malware causing the problem so getting a screenshot was difficult. 

Ive seen that post that you mentioned before but I'm unsure what to do with the information. I did try a restart rather than a shutdown just to try it and it didn't do anything. While doing the repair upgrade I used the media creation tool and it downloaded the windows image from Microsoft and the system installed updates twice and also afterwards I've installed updates for windows 10 and defender. The last update I installed was kb5000802. 

Many months ago the computer crashed on me and I eventually found out that there might be a issue with the RAM but I haven't had any problems since. If the RAM is bad could that be causing the corruption during the repair upgrade or after? Or is that not likely? I've run sfc /scannow again but it didn't find any corrupted files this time. 

Also after all the scans I've run (malwarebytes, microsoft scan, rkill, adwcleaner, kaspersky) can I safely say that it's not a virus or something like that? Or is that still a possibility?

Please post a screenshot of Disk Management, which I read like a doctor reads X-rays. Follow the steps here so I can see everything needed to advise you: http://answers.microsoft.com/en-us/windows/foru...

Other fixes I find for known issue of Defender Offline scan not working:

Glen's posts here: https://answers.microsoft.com/en-us/protect/for...

This was a known issue in early 2020 with Update KB4052623:

https://appuals.com/windows-defender-update-bug/ so did you use the latest version media when you did the Repair install? Check in Settings > System > About it's at 20H2.