Slow After Re-installation

Please read through the rest of my post #6.
There are things you can do.
@steve108- that was a test of max disk transfer rate where I think you're looking at CPU usage.

Still awaited:
Post a screenshot of your task manager taken a few mins after logging in when the PC should be nominally idle.
Albeit I think

Currently, all the values are near zero, bar memory at 35%.

addresses that.

Crystal diskmark:
I just found this for you:
Laptop harddisks (HDD, SSD) benchmarks - NotebookCheck.net Tech

Search through the list for a disk similar to yours.

I used Google and searched for
Momentus 5400 2.5" 1TB crystaldiskmark

There are more results from that search if you need them.Please compare your figures and post what you find.As I said, that's only indicative, not precise.

So this might indicate that the problem is not necessarily the disk.

You can get reasonable figures with Crystal Diskinfo and still have poor transfer rates, unfortunately.

And yes, as steve108 suggests, one way to deal with this is to avoid solving the issue and change the disk. Mostly the main difference I notice with one is the much shorter boot time and any disk intensive usage e.g. disk imaging (ovre USB3).

I believe at the time I would have had 1903/9(?) installed.

- the low-level drivers can change as I said before from one Windows build to another.

Example: I've seen cases reported here where with one build, audio is fine, but terrible driver-related latency after upgrading.
The driver in question was built into Windows.

- except it may be tricky....

@Matt316,

Very briefly, CrystalDiskMark provides a simplified overview of how your disk performs in MegaBytes per second. The topmost row shows how well it performs when reading (and writing) large, contiguous blocks of data, while the lower rows show how well it does for progressively smaller and more randomized reads and writes. The values in the lowest row tend to be indicative of interactive performance.

A quick Web search suggests that your disk is performing "nominally", although the high values in the second row are surprising, while the values in the bottom row do seem somewhat low.

CrystalDiskInfo is a separate program which can report how healthy your disk is. If the disk is having to do a lot of retries because of hardware problems, that might be one source of the slowdown that you see.

Thanks - disk health has already been checked.

What is your boot time with this PC with fast startup off?

And how long does it take from login to reach the point where CPU and disk use is minimal?