Thank you for the answer,
I have that set and unfortunately there is no bit that fits those weird
screws. It looks like a hex nut driver would work on those star shaped
screws but I can't find my set at the moment.
I'm still looking for the proper tool though
There are 2 sorts of 'raised round screwheads with notches round the
edge'. The common one is the 'inverse Torx' -- it's exactly the same as
Torx, but the screwhead is male and it fits into a ring spanner (box end
wrench?) or socket.
The uncommon one is 'System Zero'. The notches are smaller, the head is
more rounded and has sloping sides so you can't (easily) grab it with
pliers. I've seen these used in UK computer equipment -- one of my EPROM
programmers is assembled with them (for what reason %deity only knows).
In the UK, RS/Electromail sell the System Zero tools should you ever need
them (both as 'insert bits' for 1/4" hex drivers and as complete tools
with handles).
-tony