Solved Operating system not found error and BOOTMGR is missing error in Windows 7 Professional x64 OS on Dell XPS L321X 13 inch UltraBook (Rev: 1.0)

Dell XPS L321X 13" UltraBook came with a Dell Recovery Partition (about 12 GB) in the Windows 7 Professional SP1 x64 Operating System (OS). As I will perform an OS backup after I have updated the Windows OS and software with the latest patches, I wanted to delete the Dell Recovery Partition to recover the 12 GB hardisk space in the Samsung 256 GB PM830 Solid State Drive (SSD).

I connected an external DVD drive to the Dell XPS L321X 13" UltraBook and booted up from an Acronis Disk Director (ADD) 11 Home edition bootup CDROM. Then, I used the ADD 11 Home software to delete the Dell Recovery Partition and resized the Windows 7 Professional SP1 x64 OS partition to take over the deleted Dell Recovery Partition size.

When rebooting the Dell XPS L321X UltraBook, the "Operating system not found" error appeared. This "Operating system not found" error was due to the Windows 7 Professional SP1 x64 OS partition was not set as a boot (active) partition. I used the ADD 11 Home bootup CDROM to set the Windows 7 Professional SP1 x64 OS partition as a boot (active) partition.

When rebooting the Dell XPS L321X UltraBook, the "BOOTMGR is missing. Press Ctrl+Alt+Del to restart" error appeared. I booted the Dell XPS L321X UltraBook from a Windows 7 x64 System Repair Disc (created from Windows 7 "Control Panel" -> "Backup and Restore" -> “Create a system repair disc”). At the "System Recovery Options" stage, a prompt automatically appeared with the below message:

Windows found problems with your computer's startup options. Do you want to apply repairs and restart your computer ?

I clicked the "Repair and restart" button and the Dell XPS L321X UltraBook rebooted. However, the "BOOTMGR is missing. Press Ctrl+Alt+Del to restart" error still appeared. I booted the Dell XPS L321X UltraBook from a Windows 7 x64 System Repair Disc again. At the "System Recovery Options" stage, I clicked to select the "Windows 7 Professional (recovered)" and click the "Next" button. At the next "System Recovery Options" stage, the below message appeared:

To access recovery options, log on as a local user. To access the command prompt as well, log on using an administrator account.

I log on with an administrator account after entering the password. When the automatically "Startup Repair" stage had completed, another message appeared:

Restart your computer to complete the repairs.

I clicked the "Finished" button and the Dell XPS L321X UltraBook rebooted. This time, the Dell XPS L321X UltraBook had successfully boot into the Windows 7 Professional SP1 x64 OS. The "BOOTMGR is missing" error was solved.