Why, when starting the PC, it cannot boot and the brakes are terrible?

Question

Computers

I'll tell you from the beginning (maybe related). They brought another monitor home, worked on it for a day and returned the previous one, after which the following began to happen: when turned on, the light on the monitor blinks as if it is in sleep mode, although the computer turns on and works (they checked it remotely). I had to disconnect the cable, wait 2-3 minutes, when "no connection" appeared on the monitor, reconnect the cable from the PC and the screen worked (it should be noted that when the cable was corrected without disconnecting it, the PC could turn off without permission). Postponing this problem for later, this morning when I turn on the PC I see that it is not loading (the button on the system unit is flashing and it is impossible to use it, the brakes are wild). What could be the problem? What to pay attention to? How to check this or that problem?

Answer 1

If the monitor was changed, then there was a problem with the monitor? (maybe this will make it easier to understand)
The very cunning behavior of the computer hints that there may be not one problem, but two different ones .
I would start by checking disk activity (via system resource monitor) and checking disk health (SMART status). The next step is to search for an infection (drive it away with a free anti-virus scanner). Well, on to the circumstances.

Answer 2

Classic crumbled HDD, for replacement (of course, you can do a remap, but this is a temporary solution)

Answer 3

Solve the problem with the monitor separately, the problem with the hard drive separately.
At the monitor, replace the cable if it is removable, at the computer, replace the hard one.