When troubleshooting issues with Postbox, sometimes it is necessary to create a new user account to determine if the existing account has settings or third-party applications that are conflicting with Postbox. The following articles explain how to do this:
Once the account is created, log out of the current account and log into the new test account. Then, launch Postbox (install a new copy if necessary) and test to see if the problem persists.
Vista: Create a new user account