Hy, I have some problem with my new PC

Recently I just bought a new PC with the specification :

Processor, Intel Pentium Dual Core CPU E2160 1,80Ghz
Memory, Leam, 2 GB (1 GB for 1 slot)
VGA, ATI Radeon X1550 Series 512MB
Sound Card, Via High Definition Audio
Motherboard, only know the brand, ENPC

The problem is, my spec is already so high. But why I still have lag while playing some heavy Direct 3D game??? There are some games I got lag, and some not!!

Warcraft III, got no lag at all no matter how high the setting I adjust
Transformer, Got lag when destroy enemy (the explosion make it lag)
Counter-Strike, this one you know it, no lag at all
Audition, No lag at all
GTA San Andreas, No lag at all
Vampire The Masquerade Blood Lines, NO
Winning Eleven 9, NO

Nah my favourite game, Seal Online, got me full lag when using the VGA setting at Hardware Vertex Processing. But when I use Software Vertex Processing, the game run faster, but when there are many player in my screen, and also a long distance view, got me lag again.
I wonder why it like this, any idea why??? can I solve the problem?

Dual Core @ 1.8GHz isn't too high, but it should be able to run Seal online...
but to the point, about 80% (around that)of the game processing comes from the video card...it's definitely a start, maybe you should go look into that..

When playing seal online using my video card, it give me full lag. But, when I unplug the video card, n play seal online with onboard VGA, no lag at all!!!
but the other game lag!!! only seal online not lag. I wonder why it like this
Onboard VGA is NVIDIA GeForce 256MB, got HTT n become 512 MB

AH HAH!
I knew your problems lied within your video card...XDlol
if you are overclocking, maybe you should tone it down, because sometimes that might be your problem...But I have no idea why your video card is acting like that...imcompatebility perhaps? although to what extent I have no idea...
If you have recently purchased your computer, try going to the shop to ask about it..hmm

well already asked, he say that the problem lies with my game, not the computer or VGA.
NOTES : No overclocking in my PC

hmm, it can't be the game, because when you take out your video card, and use your onboard one, it works fine...
gah, too technical haha...

Thats what i think. I know that the one I ask doesnt know what actually causing the problem, so he answer the game is the problem. He only know that yeah, he already got lot of money from the computer I bought. Doesnt wanna help me. Thats all.
what a bullsh*t man he is. I think i cant get anymore info from the shop. They dont wanna care about anyother problem, except if my computer broken down XD

man Blast..Few days ago I bought this HP dv9815tx laptop with these specs
Core 2duo @2.60GHZ 64bit Vista Ultimate
4GB ram (two 2GB rams)
Nvidia 8600M GS for 512mb dedicated memory
high def audio
650GB hard drive
blue ray drive and so on..
and the native resolution on this screen is 1440x900 (I know, its shithouse =X)
and I tried playing this game command & conquer tiberium war
and the recommended specs are only 125mb and I get a full delay, and the units move like they are in matrix...(real slow) and when I build buildings and units, things that is suppose to take 4 seconds(says so on the icon) take 10 seconds to build, and it's really unplayable.
It only becomes playable when its on VGA resolution 800X600 and everything is on medium settings...I'm like WTF...I spend nearly 4000 on a laptop and it can't even play C&C..
I'm thinking on overclocking my video card, since I got no other options...
but I was wondering if you knew any other options? Maybe I should downgrade to windows xp or something...as 64bit vista might be a tad too new..or even 34bit

And yeh, I haven't tried any other games apart from warcraft...because I have no other games lol only bought the C&C when I got my laptop

I think we are in same situation. Although our computer spec higher than the minimum requirement, we still unable to play it smooth. You want to overclock your video card, I think that will not help much since the problem is still unknown. We can't guarantee that the problem lies with video card. Because playing the other game is normal, only some game with some resource got it lag.
But anyway, you can try to overclock, who know that will work ^^
I still seek for a solution for this problem @_@