I've just liberated a Clarion CD player for my 2000 Rapier to replace the standard Tape Headunit.
Anyway it's a standard unit that came with a higher spec car but when I power it up it gives out a continuous bleeping sound.
Read the handbook which advises units can not be transfered between cars.
Yes all headunits are made to work to a chasis number to stop theft etc. You need the chasis number of the pug it was out of to sort it. Local pug dealer can sort it for around £25.
You will need your car connected to a computer if you have the right software you will be able to do it yourself. My friend payed around £20 to £30 for his to be done at a pug dealer.