My pc has some serious problems.

[Calimano]

Well hello, just one year ago, my pc used to run high spec games like Rainbow Six Siege at the highest settings at 140 fps, with 0 drops. Now, my pc at any settings (Idk why but no matter the settings i get the same fps, and same fps drops) goes at around 60 fps, but has huge drops to 2-10 fps. I dont know what happened in between, the only thing i changed was my hard drive from a 500gb one to a 1Tb.
Specs: Nvidia GTX 980, AMD A8 5600k, a HyperX 8gb ddr3 ram (1 stick), 1 main hard drive of 1tb and a second one of 500gb, a 650w power, and a Gigabyte mother board.

 

[atljsf]

reinstall pc

a good clean of pc and check the psu, dust off everything helps

 

[Calimano]

reinstall pc

a good clean of pc and check the psu, dust off everything helps

Actually along the way, my pc broke (When already my games where lagging) and i reinstalled windows and my games were the same, also i recently cleaned it.

 

[Calimano]

reinstall pc

a good clean of pc and check the psu, dust off everything helps

What do you mean with "check the psu"?

 

[thx1138v2]

Run it with the side cover off. If it improves at all you've got a cooling problem of some sort.

 

[Calimano]

Run it with the side cover off. If it improves at all you've got a cooling problem of some sort.

Actually i use it like that, plus i've got two external mini fans that shoot cold air inside the machine.

 

[kgt1182]

Most importantly huge FPS drops are either your CPU or GPU overheating and slowing itself down to prevent frying themselves. Maybe your cooler was knocked off and need a reseating?

That is a powerful GPU paired with an underpowered CPU, but still you should check your NVIDIA graphics control panel, make sure you dont accidentally select SSAA for antialiasing. Also check using CoreTemp that your CPU is not overheating past 70°C. If so clean your heatsink.
Also maybe by reinstalling Tom Clancy Rainbow Seige you (maybe) got the updated version with more intense graphics/physics which tax the GPU/CPU more. If that is the case maybe your CPU might need an upgrade, or check your RAM using task manager; if its full while gaming you need a RAM upgrade