Should I upgrade?

[Selestial]

I have an old HP Pavilion DV6-7029wm with an AMD Vision A8 4500M back from I believe 2009. There's no gpu in it other than what the cpu can provide and 8 gb of ram. When I boot the computer, it takes about 1 minute and 40 seconds to load pretty much everything so I can start using it, but the hdd usage stays at 98% to 100% for around 5 minutes and then goes to 0%. I have a WD Blue 1tb ssd I could put in it, but I could just as easily put that into my i9 9900k build adding to it's already 2 tb of storage. I'm at a crossroads here with the laptop and need help deciding whether I should put the SSD in the laptop and obviously make it boot and run faster, or would the AMD CPU mentioned severely bottleneck any improvements? I should mention what the laptop is already capable of doing as is. I can run Minecraft with a few mods and Sildurs shaders high on 1080p at an average of 15 fps, but it takes between 5 and 20 minutes to load the game from the time I click on it. I can encode 1080p videos with Windows Movie Maker without too much waiting for a longer video. Honestly, I have another laptop that is far faster and counts as it's own almost up to date workstation/gaming machine, but this is just an old relic laptop I still have from college and want to keep it around but I'm a bit torn. What should I do with the TB ssd? Is it worth putting it in the laptop? I appreciate anyone who takes the time to read this.

[Exaco]

Up to you what works best for you.

But as a rule every computer has to have SSD as OS drive, there obviously would be no bottlenecks, your HDD is bottleneck + it's unclear if the HDD is even good anymore.
You can download HD Tune Pro and run the "Random Access" read test and "Error Scan" to see if there's issues, if the random access has a lot of 150ms-200ms+ reads then the drive is bit too slow.