I would like to mention that I have solved my problem of not being able to log into the system's BIOS. This is because how the nvidia is configured. Since the system uses the embedded video controller for BIOS display, the nvidia card has to be disconnected. Therefore I am marking this thread as solved.  Many Thanks  Sohaib 
Dear Dell Community,  I am new to the dell community. Recently I procured a new dell r720 server with two intel xeon six-core processors, 64 GB RAM, 2TBx4 SAS HDD with PERC H710P and an Nvidia Quadro K2000 GPU. Since the day it has arrived we have been able to successfully install CentOS 6.6 OS and every thing seems to be working fine. However, I would like to know as how I should proceed with the following matter: During boot when I see the dell logo and the progress bar on my screen, if I press the F2 key to enter the system options, I get a blank screen with a cursor blinking in the top left corner of my screen. The system stays in this state until I power it off by pressing the power button or restart the machine by pressing Alt+Ctrl+Del.  The same thing happens when I press the F11 key for PXE boot. During boot when the system prompts to press the Ctrl-S key for network options and the Ctrl-R for RAID options, I can successfully access the network and RAID configurations. If I insert a dvd and press no keys during the boot for accessing any options, the machine reads the dvd and I am able to install my OS.  Is there some setting which need to be made or is there a hardware fault. How can I diagnose this issue? I hope I have expressed issue clearly. If any further information is required please do not hesitate to ask. Best Regards Sohaib 
Black Screen