How do I unscrew these (laptop) screws I can't get a grip on?

I can no longer get anything to appear on the screen of my laptop, and tech support told me to screw open the case and press something in firmly again. My problem is that I for the love of God can’t get a grip on these things! The screws are quite small, the laptop came with a tiny screwdriver that’s supposed to fit, but doesn’t really get a grip. I managed to unscrew one screw by means of a sharp knife, but that doesn’t work for the other two, unfortunately.

Are there other (cheap and easy) ways of removing screws?