The question lacks a certain clarity...
plugged in another (another what?)
and it popped,(what popped?)
there was a 15amp (Fuse holder or fuse wire?)
in a 5 amp fuse (holder?)
Are you running power wiring on a 5A fuse?
Are other sockets on the same circuit working?
Have you measured the voltage?
Are you still using the extension lead you mentioned?
Peccavi
August 2009