1. USB mouse / devices problem
2. Sound card hardware acceleration in dxdiag.exe
3. OS problem
However, none of the above is related to my choppy problem. Finally I formatted the hard disk and install Windows ME (I was on XP before) then I found that the game can be run smoothly. Since I don't believe that the game can be run smoothly on ME but not on XP, so I formatted the hard disk again and this time install XP. You know what? The game can be run very smoothly on XP now!!
Then I started to install the applications such as Microsoft Office etc... I tried the game just after I installed any new software application every time. The game can still be running smoothly.
Until after I installed Norton System Works 2003 (Chinese Version), the game becomes very choppy. Then I tried to uninstall Norton and tried the game again. It is better, not as choppy as with Norton installed but not as smooth as before (at the time that Norton never install) too.
So for those who have installed Norton System Works 2003, if you find the game is choppy and you cannot figure out what is the problem, it might be the Norton problem as in my case. I am planning to format the hard disk again...
