It's a Dell file. See this for more info:
http://www.slipstick.com/emo/2007/up070315.htm#2

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Jocelyn Fiorello
MVP - Outlook
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> Often when re opening a meeting in outlook calandar and re saving a weekly
> recurrence is automatically made. Am I doing something wrong or is there a
> glitch in the program? I have Outlook 2007.