I’m not sure. How do I find out what I have? And what is boot? 

You have a HDD as your boot device.

it will always be at 100% because its always spinning to get data off the platter.

Get a SATA 3 SSD or a M.2 SSD NVMe PCIe adapter if you have any extra PCIe slots to add the Expansion card.

Heres a 1tb SSD to get you started:

https://www.amazon.com/Inland-Professional-Internal-Solid-State/dp/B08863G6PN/ref=sr_1_2_sspa?dchild=1&keywords=M.2+NVME+1TB&qid=1595644798&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUE4SkkzQ01ZR0FYMjMmZW5jcnlwdGVkSWQ9QTA4MDk2OTEyMFZCT1RUWExMUDk4JmVuY3J5cHRlZEFkSWQ9QTA1NzA3MTEzQ1FXU1dRQkVSRlJJJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

The adapter:

https://www.amazon.com/Ableconn-PEXM2-110-NGFF-Express-Adapter/dp/B01A4XZB38/ref=sr_1_1_sspa?crid=LXYX51MG66C6&dchild=1&keywords=m.2+nvme+pcie+adapter&qid=1595644857&sprefix=M.2+NVME+PCIe+%2Caps%2C159&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExTUVZS1kwWFRCRDlNJmVuY3J5cHRlZElkPUEwOTA0MjIyM1FHOEU4MFFONU1HUyZlbmNyeXB0ZWRBZElkPUEwNDM5MDk1Mlk2WUpaWFVLUE9VQyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

What do you mean by 100 disk usage.  

Do you mean you ran out of storage space on your drive? 

Or are you saying that when you load task manager, it shows 100% most of the time under the disk tab making the PC painfully slow.  

On #2, there are many possible issues that could cause this, disk errors, out of RAM, virus, third party applications, etc.  No way to tell what the problem causing this is without troubleshooting the PC. 

For that matter, my 3.5" spinning sata drive is currently at 0% disk usage in task manager. 

I don't see where he said he had a spinner in his PC but that alone wouldn't cause #2 to be 100% all the time.  

Now that’s clearly wrong. If your HDD was at 0% the entire computer would turn off because the HDD needs to spin in order to get data off the disk constantly and if your HDD is at 0% it’s probably not the boot drive in the first place and probably is the secondary drive.

Im just saying some straight facts because I have a 3.5 inch HDD that stays at 50% on average load and when it’s gathering Lots of DATA, it’s at 100% because of the reason above.

He may also have a SSD in which your Right, why would a ssd be at 100% utilization?

Thats why a Virus or something else is causing that.

Im not saying your wrong but I’m pointing out some things.

I have a toshiba dt01aca100. Task manager doesn’t always show 100%, but when I play call of duty or fortnite, it spikes. When it spikes my game lags pretty badly and this happens somewhat often. Is the SSD you recommended compatible with the Aurora r9? 

My Aurora r9- i7-9700k 9th Gen, Radeon  RX 5700 XT, 16GB RAM

Its compatible If you have a empty pcie slot to fit it in.

Just a simple look in the task manager.