What to look for when your computer starts to slow down

[Hunter_Lala]

This is less of a hardware question and more of a.... general.... question. But I'd like to know what you guys think is the best procedure to diagnose what's wrong when your pc starts to slow down in certain situations, be it immediately after startup, launching a program, or even at a seemingly random time.

I'm not really sure where to start looking so I generally look in my task manager and see what's doing what (though I usually don't do much in there since I don't have that much knowledge in what does what).

Any other comments related to making your computer faster in any way are more than welcome as I am thirsty for knowledge in the pc world.

 

[geofelt]

Actually, I think a very good question.

First of all, I think... What has changed?
Driver or os update?
New app installed?

Are temperatures up enough to cause throttling?

Have you contracted malware or possibly a virus?