fitted a new stereo an it wont hold the memory?

[blippi]

Some stereo's have bullet connectors on the perm & ignition live wires which can be swapped if need be. Check to see if yours has them, and if it has - swap 'em.( On a sony unit these are the red and yellow wires )

Although all the manufacturers opted into the ISO plug idea for the stereo's, it seems that someone got the diagram wrong when telling half the car manufacturers hence the need for swappable wiring.