what's wrong with that card? well, it's quite a bit slower than my 2-year old gf2 gts. a lot slower. it uses sdr memory instead of ddr... which really affects performance. did you get the pci or agp version? the pci version is the fastest pci video card you can get.. in case you don't have an agp slot. but if you have an agp slot, an old gf2 ti would have been cheaper and faster than that mx420.
oh, and i attached coolbits for you. just open it, and when it asks if you want to apply it to the registry, say yes. then go into display settings and look for "clock frequencies"... there will be 2 sliders, one for core and one for memory.