Dropped a screw in my notebook

[Extasey]

If it sits on the right spot, it may be able to pass current between a couple of resistors, circuts or capacitors.

Also the possibility (as stated above), that it could flick off the fan.

Really low possibility of this happening at all tbh. If your worried about it, use a magnet to get it out (magnetic tipped screw driver will do).

DO NOT USE A MAGNET IF ITS NEAR YOUR HDD. It will cause issues.