frame and speed go down

[Darkx112]

I just want to know I'm new to this I was trying Mario kart double dash and when i play grand prix it lowers my fps and speed to under 40 but over 30 but the game inst playable im using Dolphin svn r 5460m my spec are 2G ram, intel core dou 2.2g, nvidia geforce 8600m gt, windows vista ultimate 32bit. If there is any way i can speed up this game or if its the game it self that its making it go slow plz let me know thx in advance

[leet]

http://www.dolphin-emu.org/performance.html
if that doesn't help then it's because your computer is too weak