bios blank,post desktop screen blank,displays from desktop .

when i turn my pc fan works,lights works,everything works but display is blank as nothing is happening but in background everything is working even the window loads in the background but doesen't display after the window loads in the background then i it displays from the desktop welcome screen with the cursor and everything is perfect from browsing to playing games etc. the only problem is that the screen is completely blank before the desktop welcome screen(not even bios,windows loading is visible,no beep qas well).after turning i tried press f2 for boot menu but it displays blank but in backgroud bios gets on then to restart i had to press esc key and then Y and enter to exit the bios with my personal experience and it gets restart.

following are the specification

'''inter core i5 4th generation

gigabyte motherboard b858m-d3h-a

8gb ram

1tb hard disk

windows 7 ultimate operating system'''

i tried re inserting th ram by cleaning the dust

i tried removing the cmos battery for 2 hours and placed it back

i tried replacing a new cmos battery

i tried updating all the driverbut nothing works please help me and please explain the problem solution in breif sir so that i could fix it as soon as possible as i need to access my bios