De Use o IMAP do Gmail no Microsoft Outlook 2007 , que talvez ainda aplique ao Outlook 2010:
The reason you cannot get rid of the default Personal Folders that Outlook sets up for you is because Outlook makes you have a place for your contacts and calendar. Since the IMAP protocol doesn’t support “special folders” (i.e. contacts and calendars), you must leave the Personal Folders data file there. The only way I know of to get rid of it would be to use Exchange Server because Microsoft’s MAPI protocol for Exchange Server supports special folders for contacts and calendars.
De acordo com o acima, e já que o gmail absolutamente não usa o Exchange Server, a resposta para sua pergunta é infelizmente negativa.
Se lhe incomoda que a conta padrão ainda esteja lá, o seguinte texto da mesma fonte explica como definir a conta do Gmail como padrão:
In the folder menu on the left, Right click on the gmail inbox and choose “Add to favorite folders”. Then go to the “Favorite Folders” Group, above the mail folders, click the gmail inbox you just added, and drag it to the top of the pile, that way it will open as the default every time.
If you go to “Tools” and choose “Account settings”, click on the gmail account and then click on the button above that says “Set as default”.