i mostly use photoshop for digital painting. when i use a complicated brush type it lags badly.
what do i need to upgrade to resolve this.
i5 3570k 4.5mhz
8gb 1800mhz ddr3
Your hardware is sufficient. Update your drivers and configure them accordingly. Other than that "complicated brush type" could imply large brushes with lots of randomization and pressure sensitivity options and well, some of that stuff may just take a whiel to calculate. You wouldn't see any difference even on the latest core7i oir whatever then...