Why I am not able to boot system in Gui mode with custom xorg.conf file ?

Issue

• RHEL6 virtual machine hosted on Windows 2012 R2 Hyper-V server. But Xorg server failed to start on this system.
• Following is the error msg, shown in Xorg.0.log:

[    24.761] vesa: Ignoring device with a bound kernel driver
[    24.761] (WW) Falling back to old probe method for vesa
[    24.761] (EE) Screen 0 deleted because of no matching config section.
[    24.762] (II) UnloadModule: "vesa"
[    24.762] (EE) Device(s) detected, but none match those in the config file.
[    24.762] (EE) 
Fatal server error:
[    24.762] (EE) no screens found(EE)