Inspiron 1501 doesn't run 3D applications, except when it does

Whenever I try to enter the game world from the shell of Silent Hunter 3 or Microsoft Flight Simulator X, something very odd happens - in SH3, the mission loading screen freezes, yet the game continues to load, and after a few minutes the in-game sound will play and the game will respond to keyboard input, but the frozen loading screen remains in place.  Alt-tabbing to the desktop and back does not refresh the display.  In FSX something simliar will happen - the game world will load to 100%, after which the in-game sound is audible and the game responds to keyboard input, but again just a black screen is visible. 

And yet Red Orchestra (Darkest Hour) runs without any problems whatsoever. 

SH3 and FSX ran fine on this computer before I replaced the hard drive and did a fresh install of Windows XP Media Edition 2005.  I have DirectX 9.0c, and my computer passes the the DirectX tests in dxdiag.  I installed the drivers from the Dell Drivers CD immediately after installing Windows.  I later installed the R168684 ATI 1150 drivers from Dell. 

I would go back to an earlier System Restore point and start again, but of course none of the points I've tried so far will load.

This XP install is 3 days old and I have all of 11 programs installed - ZoneAlarm Pro Trial, AVG Free 9.0, Firefox, Google Chrome, Cookie Monster II, Foxit Reader, Steam, Red Orchestra + Darkest Hour, SH3, FSX, and Far Cry, besides the default install programs and those present on the Drivers CD.

I don't know what would cause some 3D programs to fail to work, while not affecting another, and never generating any sort of error message.

Does anyone have any idea what the problem is?

Thanks