I change my registration depending on what state I live in. Today I am a registered Republican because I am in NH and want to vote in the Republican primary.
My first registration was 1980 when I turned 18 in NJ. I registered as a Republican and voted for Reagan. Through the years I've registered as all sorts of things. When I lived in Chicago I registered as a Democrat because I was youngish and didn't care for George HW Bush and wanted to send a "message". In other states I was a registered Independent because I wanted to test the waters in the local elections.