HDD loading 100%

Question

Hard disks

Recently, hdd began to load very strongly

, I don’t understand what the problem is, there are no viruses, and I install software only from offsite sites.
OS WINDOWS 8.1
and recently noticed that sometimes the computer starts to slow down for a second at intervals of several minutes, even the light in the mouse goes out and starts to shine brightly again, although everything is ok with the light in the room, what anomalies O_O

Answer 1

You download the file to it. Why not make a screen when there is no download?
Perhaps the disk is covered a little. And just at the moment of recording, he is stupid.

Answer 2

In win7 there is a system utility "resource monitor" which shows which program writes to rl.t and at what speed, etc.
In win8 I don't know where they hid it