Dell Latitude E5550 Boot mode - HASSLE

Re-image Dell Latitude E5550 is a hassle comparing to older generations. The problem has something to do with the UEFI boot mode.

Here is what I found out to have a successful process to re-image the OS from an external CD-ROM drive. My case is using Dell Windows 7 Professional CD media.

1. Press F12 on Dell logon screen to get into the boot menu.
2. Change the Boot mode to enable legacy mode. UEFI boot will not work - no matter secure boot On or Off.
3. Boot to F12 again, select "Legacy CD/DVD drive" from the boot menu. (Booting from UEFI will result a failure during the Installation)
4. The installation will reboot the first time and it would fail. So remove the CD and select boot from the Internal hard drive.
5. Do the same step above for the 2nd reboot, and the installation this time.