Windows Vista takes care of your weekends (http://www.sandon.it/node/14)
Windows Vista changed the way it shutdowns. Developer should be aware of this change. Read at http://msdn2.microsoft.com/en-us/library/ms700677.aspx (http://msdn2.microsoft.com/en-us/library/ms700677.aspx) the rationale behind it:
"If you take only one thing away from reading this topic, it should be this one. You will be presenting the best experience to your users if your application does not block shutdown. When users initiate shutdown, in the vast majority of cases, they have a strong desire to see shutdown succeed; they may be in a hurry to leave the office for the weekend, for example. Applications should respect this desire by not blocking shutdown if at all possible."
The next time an employee of yours has a great desire his shutdown succeed because of the weekend, thanks MS if some data are lost...