For Samsung NP300E4C ..
from: Samsung NP300E5C User Manual > Page 75
Turn the computer on. Immediately press the F2 key several times.
You may just have to keep trying. You don't need to change boot-order, as generally better results can be obtained by manually selecting boot device.
More modern laptops, with Windows 8.1, do actively prevent you from accessing BIOS. But, access can be obtained through 'Recovery Menu' within Windows 8.1. This should not be an issue on your laptop (given its age).
UPDATE
Yes, I understood you were on Windows 7.
Please review: superuser.com > cant access BIOS .. on Samsung .. NP270E5V
Suggestions:
Try Esc or F10 instead;
Try FnF2 (holding down Fn, then pressing F2);
Try F2, after holding down Esc during power-on/startup;
or contact Samsung support ..