You will need
  • - small screwdriver;
  • cyanoacrylate;
  • - soldering iron with narrow tip;
  • - drill and small drill bit.
Usually on the threads of the smaller screws before tightening apply paint to increase the mounting strength. Therefore, if the head is still not fully thwarted - try to heat it with a soldering iron with a fine tip. It is important not to overdo it, because if the screws are in the plastic part of the case - they can proplavit to the screw.

After heating immediately try to Unscrew the screw - it should be easier. The main thing here is not to overdo it, so as not to derail the thread completely.
If the thread derailed completely, You will help the superglue. Squeeze glue in the stripped hole of the head and insert the screwdriver. Push the screwdriver for your screw and screwdriver. Not sutite a screwdriver until the glue dries!
After waiting some time (depending on drying speed of glue), carefully, without sudden movements, start to Unscrew the screw, gradually adding force.

Also, instead of glue you can try to drip solder, but it is less effective.
If all the above measures do not help, take a drill with a drill diameter equal to the diameter of the screw head. Carefully drill out only the head (!) screw trying as possible to touch plastic parts, in which is screwed the screw. After You disassemble the laptop (phone) portion of the screw will remain stuck from the lower part of the connection. It can gently remove with pliers.

For the Assembly screw is drilled it is necessary to use a new screw with washer (because the diameter of the holes in the plastic increased after drilling).
If these methods are not suitable and there is no possibility to use the workshop, but the unit should be disassembled, then again, take a soldering iron and constantly heating the screw head at the same time try to separate bonded parts (may need assistance). Soon plastic inner thread of the housing will heat up and fail. Method is bad because for the back Assembly you will need a screw with a larger diameter that in some cases impossible.