In bios screen my system doesnt show the hard disk as the first boot device

This means it will try to boot to the cd/dvd first. If there is not a bootable cd in the drive, it will then try the hard drive. This is the same way it worked way back when we had floppy drives, There should be a way to remove the cd from the boot list all together so it never looks at the cd to boot from(makes booting faster).