I'm not sure if it's "trained" but it sure is the way people think...ever time someone tells me that ( My PC is getting slow... I need to get a new one) I look at them like their nuts...I tell them "Your PC is not getting slow your OS is just need to be cleaned up/restored"...
A PC (hardware) never "get slow", you do an OS restore, it's as fast as the day it came out of the box
Getting a new PC for being slow is like getting a new car because you need to replace the air filter and get an oil change...
OS's need basis maintenance including occasional restore refresh depending how you use it... I restore my window box's about ever 6 mo.
Mostly this is a true statement. However, hard drives can drastically slow down sometimes as they fail. They can run out of set-aside sectors that are used to substitute for bad sectors, at which point they then are forced to retry reading/writing failing sectors that can no longer be replaced.
This can drastically slow down computer performance, and unfortunately, such slow downs are often the only symptom of a dying hard drive before it completely quits working. This slowing down can occur quite quickly or it can take weeks.
One way to tell if it is happening is if there are periodic and abrupt temporary stoppages at the same time the drive activity light goes on solidly. The worst version of this situation in Windows is if a failing sector occurs in one of the registry files.