in some games where the computer is being pushed to it's limits trying to keep a smooth frame rate..reducing to 16bit can make things a tiny bit easier on the system/vid card...likewise some games have a preference for running in 16bit,it can be a workaround for sometimes glitchy software or compatability issues...this is all games tho where "real time" is all important... for graphics/3d/surfing/whatever...crank whatever card you have as high as it'll go..if there is a performance hit working in these areas it'll be small enough that you'll never notice it..and if you do,you have much bigger problems to address and upgrade out of first...there's no sense in paying for a video card or other equipment and then depriving yourself of it's full capabilities[whatever they might be]