Yes, three passes are usually enough to give an inidcation as to whether your memory has faults.  If you did not get any errors while running the test then you can rule out memory as a problem.

Video cards and the drivers are usually the next big problem.  This is a very complex subject, since the make of the mobo and the drivers used and installed are important in relation to the driver version of your Video Card.  

Example and older board uses VIA mobo drivers 4.43.  VIA indicates that your mobo you should not use drivers above 4.45.  Your Video card maker uses Card Drivers compatible with 4.40.  You install a new game and the game manufacturer says download and then install the newest 5.6 drivers to get the best of the game.  Unfortunately, when you do you may find, the video card works, but now the system is unstable.  Catch 22.   

So comparing what your mobo, video card, and game require is important in addressing how stable the system is.  The next consideration is the BIOS setup.  VIA, and many other chip makers will tell you what to turn on and what to disable to make the system more stable.  Some cards can use Agp fast writes others cannot, etc.  

As I mentioned this is not an easy take to diagnose.  It takes a lot of time and patience.  Use email Tech support for all of your hardware to see if there is a fix.  Someone may have a remedy.

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