Installed New CD/Radio in a Astra MK4 T reg. Fob Problems and Beep sound?

Hi Guys.

Im very new to this so i hope i can explain this as best as i can.

What it is, is that iv just got a Astra MK4 that had the original rado in it but was not connected and i was told that it dident work anway. So 2day iv gone and got myself a new cd/radio and intalled it. As it is the cd/radion works fine and i can get all the radio channels and the cd works 2. but as soon as i open the drivers side door a long continuous beep comes from the dash and when i close the door it goes off. also when i try and lock the door with the key fob it will not work but i can lock it using the key, but i can open it with the fob. (Odd) i diconnected the radio and every thing goes back to nornal the fob works and there is not beep sound.

just wonted to know if anyone has come across this before and this there a solutaion. if there is i would be very greatful if you could help

Many thx
Ben