I have a Intel Core 2 DUO 2.13ghz and 4GB Ram with Radeon X1300 256 MB,DDR2, Core Clock 594 MHz, Memory Clock 396 MHz. I play Left 4 Dead and have all settings on High but Shader Detail at Medium and runs smooth but if i raise the shader to high or very high it runs slow. Is it my Video card making it do this or my Processor?