You're gonna be bothered by how cool I am.

Yeah, in my state, the Republican primary is closed while the Democratic primary is open. You can register as a Republican on the spot if you're unaffiliated and want to vote in the Republican election (unlike some states where you must have registered for a party by a certain date before the election), but I'm a staunch independent and therefore refuse to do so. And I don't really like either of the front-running Democratic candidates. So I didn't vote in the primary on Super Tuesday.

But yeah, in the general election, party affiliation doesn't matter at all (although you can vote a straight ticket on party lines. I never do this--unless you've really done your research and decided that you do indeed support only Democrats or only Republicans in every race, it seems like a particularly uninformed way of voting), and you can always re-register with a different affiliation if you decide you don't like your particular party's ideology.