Impossible to name.
I was buying tapes or more so having mom buy me tapes of my favorite bands when I was very young, mom was a music freak much like me.
Earliest shit I can remember actually playing regularly would have been Kiss Destroyer, and Alice Cooper Goes To Hell.
The first casette tape I can remember actually giving someone money for or buying was Minor Threat and Misfits but I bought them from a buddy not the store, but same thing.
<img src=http://timebombzine.metropoliglobal.com/discos/portadas/minor.jpg border="1">
<img src=http://www.punkbands.com/lyrics/bands/misfits/albums/walk.gif border="1">
I was 12.
First CD I ever purchased was AC/DC Back In Black.