Unable to delete my account - says user ID and password don't match

I've been trying to delete my account.  I've never used this account since I first opened it a month or two ago.   Today,  I followed the instructions, entered my password (it doesn't provide a place to enter my ID) but a message says that my User ID & password do not match.   So I go into my account and change my user id AND my password.   I'm thinking it's gonna work now, finally!  But I try it again and it still tells me my USER ID/Password doesn't match.   

 

Why does it tell me that when it doesn't even give me an option to enter a User ID?  I was using the same password I used when it set it up only a few months ago.   Since I'm already logged in, I go into my account and change BOTH my User ID and my Password.  That should fix it, right? 

 

NOPE.  It still tells me the User ID and Password do not match.  I've been trying to get this account deleted for days.  When I communicated with Dropbox by email to ask them to delete it, they told me I have to delete it myself.  WTH??   I've tried everything now.  Why can't I get this stupid account off of my Desktop PC?