Help for GH games?

[inogani]

i have the new pcx2 1.0.0 emu, and me and my girlfriend are playing guitar hero 2. but in the game, sometimes it will run to slow and a bit of lag then later on it will became super fast, i don't know what to do, can anyone please help me?

my pc specs :
Intel Core i3-2100 CPU 3.10GHz
2g RAM DDR3
ATI Radeon HD 4650

thanks in advance