Just like the above has written. If, for example, you're going to hang up a picture, it might not matter much if you drill a new hole next to it. Another option could be to use a so-called "grispick," see the attached link. http://www.biltema.se/sv/Bil---MC/V...ing/Avdragare/Skruvutdragare-5-st-2000016851/
Available at several hardware stores, etc.
Good luck.
Drilling into an old screw is not always the easiest task.
One option is to drill away the concrete around the plug and remove it. Afterwards, fill it with some mortar and then start over.
I used a simple pair of pliers and twisted with just simple hand force.
The same method to remove the screw isn't so bad if it's not too far in. Use a pair of nippers. You may of course need to widen the hole a bit to access it.
Fel av Åke said:
Another option may be to use something called a "grispick" see attached link.
[link]
Available at several hardware stores, etc.
Don't do that, such a slender wimp can withstand almost no torque at all. It's almost guaranteed to break, and since it's hardened you'll have an even worse problem on your hands.