have you installed 915resolution
resolution modification tool for Intel graphic chipset
915resolution is a tool to modify the video BIOS of the 800
and 900 series Intel graphics chipsets. This includes the 845G,
855G, and 865G chipsets, as well as 915G, 915GM, and 945G chipsets.
This modification is necessary to allow the display of certain
graphics resolutions for an Xorg or XFree86 graphics server.
915resolution's modifications of the BIOS are transient.
There is no risk of permanent modification of the BIOS.
This also means that 915resolution must be run every time the
computer boots in order for its changes to take effect.
If you want to automatically set the resolution on each boot
and before X is launched, see /usr/share/doc/915resolution/README.Debian
for information about configuring the provided initscript.
yum install 915resolution
also try defining a monitor ( that matches your hardware) in display settings