QuickBooks seems to remember the last user name that was used, regardless of the company file. I see this all the time when working with client files: If I use "Sally" as the user name to open a file, then close the file and QuickBooks and then come back later and start to open a different file, even where "Sally" isn't a valid user, that's the default anyway until I change it.
I didn't know it carried across windows user accounts, but am not surprised. Intuit doesn't think things like this through very carefully, much less test. QuickBooks probably saves the value on the machine related to the installation, not the windows user.
