The reasons behind system booting failure:
1.Hard Disk Not Detected.
Steps to detect Hard Disk
A) Cable Connection
1.Check if the ID cable connecting Motherboard and Hard Disk are connected properly.
2.Check if the power supply cable from SMPS to Hard Disk are connected properly.
(Sata Cable )
1. Check if the ID cable connecting Motherboard and Hard Disk are connected properly.
2. Check if the power supply cable whose output is different is connected properly between SMPS
and the Hard Disk.
B) Hard Disk Jumper
1. It holds four slots namely primary,secondary,primary flave,secondary flave.
2. If you want to connect one Hard Disk connect it to the primary slot,if two Hard Disk then to the secondary slot.
Steps to check if OS is working fine or corrupted
If Hard Disk is detected,then OS may be corrupted to fix it ,do the following.
1.Press F10 and then Last Known Good Configuration is displayed,select it and press Enter Key by which
system can be booted
2.Press F8 and then it goes to safe mode ,click enter in safe mode.This helps to boot the system.