Will not boot - Acer Extensa 4620 Notebook

If you have to select the boot device every time, this means that the BIOS (CMOS) setup does not have the boot device listed as the first device to boot from. At startup, press the key that enters CMOS (BIOS), usually DELETE, or possibly F2. Once in the CMOS, look for boot options, then boot devices, then boot sequence. Find your device and ensure that it is listed first in the boot order sequence. Then save the changes and reboot. You may have it set for a USB or network boot first and it won't boot without intervention.

Boot sequence problem? You set the boot sequence permanently in the Bios or System Setup. Normally when you boot the system the screen will tell you what key to hit to get into the Bios or Systems Setup.

You can set the boot sequence temporarily (just for the current boot cycle) by watching the screen when you boot and it will tell you which key to hit to change the boot sequence or boot order.

Yes. It is called "Dual Boot" or "Multi-boot". You can even have different operating systems on each drive or partition. For more information, just click this link.

Because the BIOS is probably set to boot the hard drive first. The A drive, second or third depending on the boot order set in the BIOS.

Hi,
You must change the boot sequence from your BIOS.
To do this, when your computer starts press F1 or F2 until you enter the bios setup menu. Usually on Toshiba is F1 or Esc key.
Now that you are in the BIOS, you must locate the boot order section. Just go through every page until you see something like Boot Device, Boot Order, Boot Management, Boot Sequence, etc. (its different for each computer)
There, change the boot order to move the Hard Disk or DVD ROM in the top two items in the list.
Save your settings and exit the BIOS.
Your computer will restart and it should boot up normally.

Set all in Boot priorty to CDROM
Set Other Boot Device to No.