Not a computer issue as such, but a hands-in-the-air-what-the-world-has-come-to kidna comment.

I've got a 15 year old computer which I purchased a couple of years ago specifically to run Oblivion (with mods). It is an upgrade for an 18 year old computer which I purchased originally to run Oblivion without (many) mods. The 15 year old one is an i5 with NVIDIA GT 1060 and 8GB RAM, and it works beautifully, even despite running Windows 10.

I run Oblivion with TWMP and Morroblivion together which is like 10x Oblivion! I cannot complain.
Yet people keep telling me on Nexus that I have to get a new computer because I am so hopelessly behind the times. And I say NO. Oblivion is a 19 year old game, so if a 15 year old PC cannot run some mods, then I don't want those mods (I'm looking at you, Better Cities!). No, really. Why does Morroblivion fit nicely but not Better Cities? Methinks something is afoot with those Better Cities, actually.
But I digress. The reason I am not looking to upgrade my PC is simply cost. I just don't want to spend "a thousand or two" of whatever currency on a computer meant to run a 20 year old game.
And this is a nod to Renee: I know you're umming and arring whether to buy a whole new PC or to replace the drive in your old PC. If cost is a consideration, then don't tell yourself that you must absolutely have that latest thing and then forego eating for a couple of months. It all depends on your budget, in the end.