Can't access BIOS after booting from USB drive

Hi,

I've recently decided to install Ubuntu 16.10 on my Toshiba Satellite c-50 b-17g. Since my laptop does not have a CD drive, I created a bootable flash drive using Rufus. In order for it to run, I entered the BIOS and disabled the Security Boot and changed the boot mode from UEFI Boot to CSM Boot. That worked in order to make Ubuntu boot from the flash drive.

However, for some reason, I couldn't install Ubuntu; all I've managed so far is to run it from the flash drive, but that's not the main issue I'm facing right now. I still want to be able to use Windows on this laptop; however, after I've changed the BIOS settings, I haven't been able to boot to Windows.

Everytime I turn on the computer, it goes directly to Ubuntu Boot, if the flash drive is in the USB port; if it isn't, I get the following message: PXE_E61: Media test failure, check cable.

I suppose the issue is related to the changes I've made to the BIOS set-up; however, now I'm unable to enter the BIOS in order to undo those changes. To enter the BIOS I would press FN-F2, but now it won't work. I've tried different keys, such as ESC or F12, but nothing seems to work.

If anyone could help me on this issue, I would be extremely grateful!