From the information you have provided, it seems this is not a default folder of Gmail and Outlook 2010.

- Do you have any rules, forwarding or filtering mail to this folder? If so try removing these rules.

- Do you have mail forwarding going to your old G mail account? This really should continue filtering email into the folder but may show why you are still receiving Google mail.

- Do you have any other Devices /Computers still configured to your old Google mail account?

Some of the following command line switches may fix your issue also. Please use caution when performing these, and be sure to use one at a time.

Windows Vista/7:

• Click Start.
• Click All Programs.
• Click Accessories.
• Click Run.
• Enter the following in the Run dialog box (with quotations):
  "c:\program files\microsoft office\office14\Outlook.exe" /Commandswitch
  
  Note: For 32-bit versions of Outlook running on 64-bit Operating Systems, you will enter the following (with quotations):
  "c:\program files (x86)\microsoft office\office14\Outlook.exe" /Commandswitch
• Click OK.

Switches:

- /cleanrules = Starts Outlook and deletes all client-based and server-based rules.

- /resetnavpane = Clears and regenerates the Navigation Pane.

- /resetsharedfolders = Removes all shared folders from the Navigation Pane.

(Lastly try opening Outlook in safe mode and remove the folder)

-/safe = Starts Outlook with all extensions turned off and without Reading Pane or toolbar customizations.

Hope this information helps you get that pesky folder off your Outlook.