Troubleshooting guide for Windows
Problems before entering the game
Graphics card drivers
Download the latest driver from the graphics card manufacturer's web site and install it.
NVIDIA: http://www.nvidia.com/content/drivers/drivers.asp
AMD/ATI: http://support.amd.com/us/gpudownload/Pages/index.aspx
Intel: http://www.intel.com/p/en_UK/support/graphics/
Make sure Windows is using the correct driver. Windows has its own set of drivers which are sometimes set as factory defaults, even when the manufacturer's drivers are available. To ensure you are using the correct driver for your graphics card, see:
http://windows.microsoft.com/en-US/windows-vista/Video-cards-frequently-asked-questions