Could someone recommend a good program to scan my computer's performance?

Preferably, it would be a program with a free license :-) My computer has recently started to lag terribly, even when I write a simple post on Facebook, I have to wait sometimes a few seconds before the letters appear on the screen. My computer is old but until recently, there were no such problems with it, I... show more Preferably, it would be a program with a free license :-)

My computer has recently started to lag terribly, even when I write a simple post on Facebook, I have to wait sometimes a few seconds before the letters appear on the screen. My computer is old but until recently, there were no such problems with it, I could even play some newer games, such as Life Is Starnge 2, Kerbal Space Program, Cities Skylines, Sims 4, or Civilzation 6, and my computer is from 2009

I have Intel Core 2 Quad 8400, 2,66 Ghz, 6 GB RAM, GPU: NvIdia GTX 750 1 Gb, Windows 10.

So can recommend my good diagnostic program, my friend who is IT technician said that it maybe it's HDD bad sectors.

I had two HDD 500 GB that hold Windows 10 and 2 TB that i use for my videos my Steam and Origin games :-)
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