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Office applications have disappeared from your Mac.
First, check if they are still on your computer. Open Finder, select Applications on the sidebar, open the Office folder and check if Word, PowerPoint, Outlook and Excel are here. If they are here, drag them to the Dock and delete the old icons.
To delete icons from the Dock, right-click them and select Options > Remove from Dock, or just drag them off the Dock.
If they aren't there, reinstall Microsoft Office. Also, open > Software Update and install the most recent Snow Leopard version, Mac OS X 10.6.8