Example 1)Graphics Card Quadro 6000 DVI Card rather than the VGI Card.
First - Remove the Graphics card then install the operating system
Second - After OS installation, install Driver for Graphics Card and insert Physical Graphics Card into PCI slot.
Example 2)RHEL6 Installation Option - RHEL6-Install System with BASIC VIDEO DRIVER
if we install without this option, while GUI Mode is staring we will not get proper display.
In that case we need to choose RHEL6-Install System with BASIC VIDEO DRIVER option.