I just picked up a new car and found out that the previous owner replaced the rear tail light bulbs with the wrong ones. I tried replacing them with the right ones but when I turned the lights on, the bulb blew. I replaced it again and turned the lights on and it blew again. This is what the bulb looks like after it blows:
http://i4.photobucket.com/albums/y146/Boarderx192/E36/Questions/Picture022.jpg
http://i4.photobucket.com/albums/y146/Boarderx192/E36/Questions/Picture021.jpg
http://i4.photobucket.com/albums/y146/Boarderx192/E36/Questions/Picture020.jpg


I took out the socket to see if it was the cause and this is what I saw on one of the contacts:
http://i4.photobucket.com/albums/y146/Boarderx192/E36/Questions/Picture019-1.jpg
http://i4.photobucket.com/albums/y146/Boarderx192/E36/Questions/Picture017-1.jpg


Whats going on and how can I fix it?

You don't need a dual stage light in there unless you have the foglight switch wired.

Put the single stage back in and be done with your problem.

If you really want an accurate idea on what's the cause then details like what taillights, pictures of the wiring, and pictures of the taillight wiring leads are what is needed. Showing us a shot of a blown bulb doesn't say anything.