Computer running slow, struggles to load the most basic of softwares

I made a thread two weeks ago when my computer would randomly turn off and restart on its own which can be found here.

I was out of town for a while and recently came back home, when I loaded up my computer everything was running super slow, even the desktop icons took a minute or two to load up. If I have more than a few tabs open, everything starts lagging and becomes super frustrating to deal with.

One idea I think may be the cause is the HDD, which is a really old one that came from my old pc which I put into my new one as I couldn't afford to buy a new HDD.

If I try to load up too many things at once, I get BSOD and that's when I thought it may be a hardware problem as well

Any help or suggestions would be appreciated!