BOOTMGR is missing press Ctrl+Alt+Del to restart
Something has messed up the ability to boot off your primary hard drive. You will need to create a System Recovery Disk on another Windows 7 system as this one is currently not bootable. Control Panel -> Backup and Restore -> Create a System Repair Disk, have a blank CD ready to burn.
Remove all USB devices plugged into the machine except keyboard and mouse (laptop so not applicable).
Check your BIOS settings for your hard drives. BIOS should recognize the internal hard drive and list it. If not, you have a cable loose or the hard drive has failed.
Check your BIOS settings for boot device priority. Make sure it shows the DVD drive and the hard drive at a bare minimum and that the DVD drive is listed as the first item, followed by the hard drive.
Insert your Windows 7 System Recovery disk in the DVD drive and boot into System Recovery (Repair your computer) and select the Startup Repair option. Try rebooting.
If that didn't do the job, reboot off the Windows 7 install disk into System Recovery and this time, select the Command Prompt option. From the command prompt, run
bootrec.exe /fixmbr followed by
bootrec.exe /fixboot. See if the computer will boot.
Use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair startup issues in Windows
And for your information, USB based devices are removable and will not be showing in your BIOS. You can enable booting off them in the BIOS but they're peripherals, not internal devices.