Run as different user error with Dropbox

Hopefully this is the right forum to post in, my apologies if its not.

I'm trying to run Dropbox as a different user, but whenever I try, I get the error "Logon failure:unknown user name or bad password." The first way I tried was by holding shift and then clicking "Run program as another user." The username and password that I typed in were definitely valid, but for some reason they weren't recognized as so.

So I tried another gimmick, I installed Dropbox on the alternate user on C:\ and navigated to "C:\Users\(user)\AppData\Roaming\Dropbox\bin" on my administrator account. I then made a shortcut of the .exe to desktop, went to properties, and added in "runas.exe /user:username" before the target. Command prompt then came up asking for a password, and when i typed it in, the error "RUNAS ERROR: Unable to run.... 1326:Logon failure: unknown user name or bad password."

I'm clueless, someone please help me out! Thanks! :)

Here is our tutorial on the subject, hopefully you will find some hint that may help
Run as Different User

It appears,however that it describes the procedure that you already tried.

OK, at least we have confirmation of exactly what was tried and that a problem exists. Maybe, this will correct it.SFC /SCANNOW Command - System File Checker

Have you tried creating another User Account just to test that it is the computer, and not a dodgy User Profile?

haha, your welcome :)

Never let it be said my random shots in the dark don't work