Hi Barry, it is a security screw head used to stop non techs from getting into dangerous or non servicable by layperson areas of equipment. it is a torx screw you are looking at. If the door of your oven will not open, assuming it has the usual 2 hook latches, these are the bits that stick out from the door and for the latch mechanism that allows the unit to operate when the door is closed, then simply take a pallet knife in your right hand, grip the handle with the "blade" verticle pointing upwards, and the flat surface facing you , gently insert the pallet knife between the oven face and the inner part of the door under the lower edge of the door, and keeping as close to the keypad edge slipp the knife upwards and it will hit and release the door catches. In case we have a "continent" problem here a pallet knife is a kitchen implement used to lay icing flat on a cake. a slim paint scraper or similar thin tool will suffice. Once open you can ascertain whether the catch is faulty or the reciever. Both require a degree of knowledge to fix. Whatever happens please remember you are messing around in a piece of equipment that runs at 4000volts and due to the design of its circuitry under certain fault conditions it remains lethal months after having been disconnected from the mains supply. its not rocket science as they say, but it is not for the layman either. Contact me via microwave-repairs.co.uk if you need further help.
patrick, August 2009