CPU usage 100%

[Caledonia3]

CPU is constantly running at 100% so it is extremely slow and, latterly, unusable.

This has been ongoing for >1 year, I have managed to fix it temporarily throughout that time by doing some things I read online. Eventually I had to do factory reset which solved the issue for a short while but now it's worse than ever. 

I save all files to a cloud server so minimal are on the laptop itself. I mainly use the laptop for basic, everyday tasks such as browsing, Microsoft Office, occasional streaming and photo editing.

I have a OneDrive account and have to pause syncing to be able to browse however this is now impossible even with that temp solution.

I gave up and looked at buying a new one but I see many are still a similar spec to the one I've got except for the hard drive as newer models are using SSD.

Specs for this laptop are:

8 GB DDR4-2133 SDRAM (1 x 8 GB)

Intel® Core™ i3-7100U (2.4 GHz, 3 MB cache, 2 cores)

1 TB 5400 rpm SATA

Running Windows 10 64bit

I bought it just over 4 years ago. Can you tell me if it's worth upgrading to an SSD, or doing something else that would improve performance? Or would I better buying a new one with the same spec but with an SSD, or going for an i5 processor, 16gb RAM and SSD? Or even an AMD processor. I need the larger screen as I use the number pad regularly and don't want to use a separate keyboard.

Thanks.

[Prométhée]

Hello
Up to you ..
This laptop could be improved, but if you can replace several elements, it is worth it for a laptop that is already at least 4 years old.
It would take more memory, possibly replace the sluggish HDD by an SSD indeed ..
If the process is also a problem, to replace also, and not always possible
the simplest indeed, will be the purchase of another computer, a good configuration, SSD but strict minimum 250go (see if you find a computer with SSD and HDD, it can be interesting to store the data)
16 gb of ram, indeed, it is comfortable!
For the processor an i5 at best i7 or higher, but if I understood the use, an i5 should suffice
see the comparative sites, to avoid unpleasant surprises