How to access the boot menu?

I'm having a bit of a struggle getting into the boot menu using the F15 key like the screen tells me to when I first fire up my PC.
It seems like the F keys aren't cooperating at all, whether I'm trying to jump into the BIOS or just get into Safe Mode. I've got a Dell motherboard paired with an Intel i3 processor, and while I did manage to successfully install Windows 10 over my old Windows 7 setup, the issue persists—those F keys just won't trigger the boot menu or the BIOS settings.

Does anyone happen to know if there's some other way to access the boot menu without relying on those specific function keys? I would be incredibly grateful if someone could point me in the right direction.

If you've got a legacy PS2 keyboard plugged into your PC, try grabbing a standard USB one instead. Once you're set up, try mashing that key right when you hit the power button until you finally break into the BIOS.
ps: have you messed around with switching the USB port where the keyboard is actually plugged in?

Doesn't matter if you mash the Del or F2 keys...

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