I recently changed my username. From other advice, I went into user and groups from system settings and rightclicked on my username and then selected advanced options then typed in a different username. I closed my computer, then later on in the day I opened it up to see a username that's my old one. I tried to type in my normal pass, did not work. I couldn't change the username to my new one, and worse I don't have guest account. help? OSX Yosemite I think latest one (can't check, I can't login), and macbook air 11, 2011.