How do i reprogram my key on peugeot 307 hdi 2001

On the 307 u have to hold the lock button on keyfob for 10 secs as follows:
TAKE KEY OUT OF IGNITION. put it back in switch on (dont turn engine over) and hold lock button on key down for 10 secs. switch off take key out making sure not to turn engine ove. once key out, should be reset. pray and try again making sure u wait the customary 5 secs for display to finish.

also shown ion mini booklet

Many cars have a different process to enabling passive systems, some require turn the key on and off 3 times then hold it in the on position while holding down the remote, or you may hear a chirp to start the calibration process, the safest way of course to marry the unit to the vehicle is to scoot down to the Peugeot dealer and get them to do the program, it may cost, but they also have to make sure everything works correctly too, so they will stand by the service they provide you. hope this helps, happy holidays.