Do you mean the 'read-write' login when you open up IT Assistant?
You can reset the password as follows:

1. Open dcdbmng.exe in C:\Prog...\Dell\OpenManage\IT Assistant\bin\ (or wherever IT Assistant is installed)
2. Click the + to expand the 'ITAssist' database
3. Select the 'Users Information (Users)' node at the bottom
4. Click the 'Action' menu and select 'Clear table'
    You will see a warning about losing settings, don't worry as you are only clearing the read-write password
5. Close the program

When you restart the IT Assistant GUI (IE) the read-write password is blank.
If you open the database management utility again (dcdbmng.exe) you'll see the Users table
is recreated.

  

This was a LIFE SAVER!  Not literally I guess, but our ITA install seems to corrupt or forget the password occasionally and I've never known how to fix it.

This is a huge help, thanks!