What are the specs on your machine... be sure to include name brands etc.
most of the time if you are experiencing video drop out either in gaming or video watching it is due to a memory buffer overflow... which you see with a lot of PC100 and PC133 SDRAM sticks.
If you have DDR... try switching the DIMM Slots your memory is in as well. You also want to make sure that in your BIOS that the AGP Apenture is set right. A lot of people leve it on 32MB even when they have a 64MB or even 128MB video card.
Try those out and get back to me john.
As to playing games I play a lot of:
Counter Strike, Day of Defeat, Wolfenstein Enemy Territory, C&C Generals