The HDD light may or may not stay on depending on the design the maker used. It's been kicked around before but we can't use it any longer for telling how much disk I/O is going on.
As to the usage, that's common with old HDDs. They are just that slow.
Be sure to lighten that load with a common setting. Read https://www.howtogeek.com/224981/how-to-stop-windows-10-from-uploading-updates-to-other-pcs-over-the-internet/
Why does the hard drive light stay on with no flickering on my Windows 10 OS?
And, in task manager, under the Processes tab, should System be using 33% of the Disk at 300MB/s?

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