Khuram_Rafiq, The first step is to drain the system flea power by disconnecting the power cables and then pressing and holding down the power button for about 15 sec. If the system boots, go ahead and update the iDRAC. If you are not able to perform this update, then you will have to update the LifeCycle Controller (LCC) or run the the LCC repair package if needed.  Let me know if you need any further assistance.
I installed windows server 2012 r2. After installation i tried to update iDRAC latest version but after installation my system was restarted. But now it stack at Initializing iDRAC few minuets and give massage Initializing iDRAC failed and restarted again and again.. System smart display and keyboard is also not working..  Please let me know how to i can fix this problem ... 
Dell PowerEdge R320 Initializing iDRAC.......