in your graphic properties, click on advanced, than the tab that says geforce4 or geforce3, whatever you have. than there will be a white menu that loads up along side the properties menu. click on nview display mode. than click device settings and color correction. that is where digital vibrance is.
Athlon XP 1.58GHz | MSI KT3 Ultra2 | 256MB DDR PC-3000 | GeForce 4 ti4200 64mb @ 310/533 | IBM 120GXP 40.0GB | Det. 41.09 | DX 9 RC2 | Win XP SP1