You can limit the number of documents displayed in the list but you cannot
delete individual documents.
In Excel or Word:
Click the Microsoft Office Button, and then click the Options button.
Click Advanced.
Under Display, in the Show this number of Recent Documents list, click the
number of files that you want to display. If you do not want to display any
files, click 0.
Tip To keep a file in the Recent Documents list, click the Microsoft
Office Button, and then click Pin this document to the Recent Documents list
.. When a document is pinned to the Recent Documents list, the pin button
looks like a push pin viewed from the top.