Windows 7 + Outlook 2007

Due to a PDA sync problem, I've ended up with holiday duplicates throughout. I see within Tools/Calendar I can select a different country but not where I can tell Outlook NO holidays (if I uncheck United States, the 'OK' button is not active) and have Outlook eliminate ALL holidays (then place the x back at U.S. to add one instance back) instead of me doing so one by one.

Is there a way to automatically delete all holidays?