I’m not trying to be mean because everyone can’t afford or are just not willing to spend their money on the best stuff available, but how old is this computer? Looking at the benchmarks the video cards that are just about enough run this game with medium/high settings @ 1080p are about 4 times more powerful than HD 5570.
What are your graphics set at and what resolution do you play on?
Naturally turning the screen demands more on the system than looking at one point, you have to render new objects constantly on the screen vs just some tiny changes in the enviroment. Fps drop from 60 to 10 while doing this made me suspect that the GPU is the culprit here. Where are you getting that 60 fps? Everywhere in the open world I’m guessing, but also in cities, like Lion’s Arch or the city you started at?
Your CPU is also on the lower end but fear not, so is mine. While yours is a dual core, it has Hyper-Threading which makes it something closer to a quad core, mine is a quad and it’s weaker at stock clocks. You will run into trouble when (or if) you try to do some World vs World with this CPU, but there’s luckily plenty to do outside that as well.
What you can do is try lowering the graphic settings, namely rendering, shanders, textures, enviroment and of course your resolution if there’s room to go lower. It will look like garbage but if it helps, you know that’s the cause and you’re lucky: changing a GPU is one of the easiest parts and the socket is universal, meaning you don’t have to upgrade any other part along with it and once you decide to do a whole system upgrade, that card will work perfectly there. Plus you’re looking at only around $100 investment to have more than capable card again! 
I hope this helps, please respond back here when you’ve done those little tweaks.
i already try that, even i set at the lowest graphic setting, at town and open world both are the same, without touching mouse i got 60fps even i hit some mobs
when i playing aion at medium based graphic set, i have no problem and some game like assassin’s creed 4 with low set. the issue when i dragging my mouse is bothering me, it is just dragging mouse’s cursor can make such effect?
oh God why?
and some strange habbit while i starting the client, when i click login and play my screen blinking and show window frame, and the first loading after selecting character it happen again. my friend told me the GPU’s drivers is the culprit, but i already at the latest version
sometimes the game run smooth without this issue at the first few hours and sometime just smooth in few minutes
yes im planing to change my old GPU next month, hope this annoying issue go away
btw thanks for replay
i just trying use compatible mode, it said compatible with win xp sp2 and i start the game and it run smooth like a butter even at medium setting