Signed up Incorrectly. Can't uninstall/reinstall or fix~

I goofed. When I originally signed-up, instead of entering my username (BrennanK), I immediately started adding friends' names (Ed_Dale, Dan Raines, Gurubob and Cybercoder). Now I cannot access the program because those thwirl accounts keep coming up. I don't have their passwords (and shouldn't) but even after uninstalling and re-installing, I can't get past those four names to install my own. Can you help me?