Office 2007's secret kill switch
Microsoft’s battle with pirates, which started as early as 1975 with Bill Gates’ infamous “Open Letter to Hobbyists,” continues on in 2007, as the company has built a feature into Office 2007: Reduced Functionality Mode. While Microsoft has been fairly coy about whether or not this feature exists in the latest Office release, a new Knowledge Base article on their site confirms that it will apply to all Office 2007 products.
Reduced Functionality mode is triggered whenever Office 2k7 fails activation. This can happen when the program is initially run after installation, or if it fails a subsequent check following an Office update. Once the switch is thrown, Office continues to run, but with the following restrictions:
You cannot create new documents.
You can view existing documents. However, you cannot edit them.
You can print documents. However, you cannot save them.
Full article: Ars Technica