From Use Gmail IMAP in Microsoft Outlook 2007, which maybe still applys to 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.
According to the above, and since gmail does absolutely not use Exchange Server, the answer to your question is unfortunately negative.
If it bothers you that the default account is still there, the following text from the same source explains how to set the gmail account as the default :
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”.