My computer is load, seems under big load...On the desktop?

LiViAqC

So I bought this computer, and since the very beginning when I installed Windows, I felt like something was off  : Is 8 hours normal for an installation of Windows?
Plus, whenever I have more than 5 pages on Firefox, they shutdown OR the computer is super duper slow.

I'm really sad that this computer is not performing well, althought the critics was quite decent.

Is my computer having a problem, or is it just its real performances? Knowing difference would help me decide if I repare or I sell it.

Thanks in advance.

p.s: English is not my first language, sorry for the mistakes.

LiViAqC

is under load *