windows 10 disk performance always in 90's

1. Not at all normal for Windows 10. My disk most of the time is under 10%; CPU under 5%
2. factory reset pc  - It may be trying to get to Build 1511 Version 10586. That is 3 GB to download and set up to install. What version are you running.
3. What was the base operating system for the factory reset?
4. Nothing on it  - so no applications yet or anti virus yet.

Let it run overnight and see in the morning if it has done updates.

If nothing above applies, are you sure the machine is made for Windows 10? Might there be a hardware problem? I would get the Dell Support hard drive tool and check the hard drive very carefully.

first try booting into Safe Mode with No Networking support as this will not load most non-essential services. observe any changes on disk activity.

what's the computer's spec? does it have sufficient RAM? is the disk SSD or SATA?

i would start by running a diagnostic on that drive - to be sure it does not have problems
i use the UBCD for this :
Hardware diagnostic CD    UBCD
---------------------------------------------------
go to the download page, scroll down to the mirror section, and  click on a mirror to start the download
Download the UBCD and make the cd   <<==on a WORKING PC, and boot the problem PC from it
Here 2 links, one to the general site, and a direct link to the download

since the downloaded file is an ISO file, eg ubcd527.iso - so you need to use an ISO burning tool
if you don't have that software, install cdburnerXP : http://cdburnerxp.se/

If you want also the Ram tested - run memtest86+ at least 1 full pass,  - you should have NO errors!
 
For disk Diagnostics run the disk diag for your disk brand (eg seagate diag for seagate drive)  from the HDD section -  long or advanced diag !  (runs at least for30 minutes)

http://www.ultimatebootcd.com/      

**  you can make a bootable cd - or bootable usb stick
*** note *** for SSD drives  use the tool from the manufacturer, like intel 's toolbox :
https://downloadcenter.intel.com/download/18455/Intel-Solid-State-Drive-Toolbox

for completeness -here's how i handle disk problems : https://www.experts-exchange.com/Storage/Hard_Drives/A_3000-The-bad-hard-disk-problem.html

As noted above, Search Indexer, Windows Defender. Old hardware could also be the cause. A computer with an SSD at 1% hdd, could very well be 90% on a really old hdd.
On older hardware, I immediately disable:
Windows Defender (let antivirus take over)
Windows Search
Superfetch
HomeGroup sharing
Xbox related stuff
Windows Media Sharing

A combination of old hardware (low memory, slow hdd, slow cpu) will always have some form of spikes in CPU/HDD usage from time to time.

My ThinkPad is 3 years old, 500 GB 7200-rpm hard drive and remains plenty fast.  I do not have to disable Indexing but Defender is disabled because I have SEP.