I set up my computer about 6 months ago with only one user (my first mistake).  I don't think I set it up as administrator (my second mistake).  I've tried going to control panel/user accounts but a blank window pops up with a weird message in the header part but nothing in the window.  I've tried everything I can think of and have looked everywhere I know to look.  Any ideas how to correct this?  I'd like to add more users and do other things but cannot without the ability to get into the User Accounts.  Thanks for your help!