How do you reset the antitheft radio for an 1999 Oldmobile Alero after the battery died?

There should be a factory reset code in the owners manual of your car. It should be located under the radio heading.If you are not the original owner, The first owner had the option to change the code so no one can use it if it was stolen.In this case, you will have to take the car to the dealer or you can take out the radio and get the serial number off the back and the dealer service department should be able to give you the factory code over the telephone so you will be able to change it back. I and Good Luck,MPAB