F12 is the key you need to hit to select boot device, you can also change boot device in BIOS by hitting F2 at the beginning of system startup and then drilling over to that area.  You may be missing that if your video is slow in starting.

 

Cheers, Dave 

Try using the F12 and selecting a one time boot device, that should work.

Cheers, Dave

Right.  I entered into BIOS by pressing F2 key. Then pressed enter on "Boot sequence". It shows the devices like HDD, cd/DVD, floppy etc. To enable the Cd/Dvd , the instruction is to press space bar but it does not work.  Also, to move the devices up/down, the instruction is to press -/+ but it does not work.

There is only HDD when I pressed F12, no cd/dvd.

One of two possibilities come to mind, 1.) The optical drive has failed 2) the BIOS is corrupted.

 

 Go here to read about clearing NVRSM:

http://www.dellcommunity.com/supportforums/board/message?board.id=dim_bios&thread.id=55387

 

Let us know your progress...

Cheers, Dave

Never mind, I cleared the CMOS and it is fine now.

 

Thanks. 

Great, please mark the solution post so others can find it.  Glad you are ok now!

Cheers, Dave