Lag/ Stuttering in Amnesia

[toni112007]

Hi all!

I have a problem playing Amnesia The Dark Descent ( Penumbra too, and some other games aswell )

Thing is i play Amnesia 98% of time at 50 fps.
But when i use Lantern ( for first time, when loading game ) it freezes for second and than continues normally, after that i can use lanter 100000 times and does not lag.
It also happens if i "for first time" move camera fastly ( fps drop for half second than back to normal )
It also happens sometimes when use tinderbox on candles ( and other stuff, forgot its name )
In Penumbra series there is camera lag just like in Amnesia.
But there is also half second lag when monster is breaks the door.
I have also lags in some other games which include explosions, fps drops for few second than back to normal.
I play Amnesia at 1280x1024 at medium settings.

My specs:

CPU : Intel E 1500 2.2 GhZ
RAM : 2GB
GPU : Sapphire HD 7750 GDDR5 1GB
PSU : Corsair VS 550W
HDD : Toshiba 500 GB 7200rpm 6gb/s
OS : Windows XP sp 3

Can anyone help me solving this?
I dont know what causes this, weak cpu or HDD or something else...