Little speed advice....

Im playing Overlord on my PC, im running a pent 4, 3 gig, 2 1/2 gigs of Kingston ram, Nvidia fx 5500 256 megs....im running coolbits and game accelerator pro 7.6 on hyper speed w/ the pure game environment enabled, i have the detail settings on low and have the display mode at 640x480 at 60hz and im still a little glitchy. I know a better video card and dual core processor would help emmensly...but i have what i have....My question is im not real sure what the "60hz" is....i have settings to change it all the way up to 150hz....would changing this have a noticable effect on my game? Also...is there a post anywhere in MajorGeeks archive that can give me some tips and tricks on speeding up my PC for gaming....such as virtual memory settings, page filing etc... thx