To clear the My Recent Documents list, follow these steps: 1. Right-click Start, and then click Properties. Or, if the Start menu is already displayed, right-click an empty area of the Start menu, and then click Properties.
2. Click Customize.
3. Click the Advanced tab.
4. Under Recent documents, click Clear List, click OK, and then click OK. Your most recently used documents are removed from the My Recent Documents folder.
even better - download and install http://www.ccleaner.com/download
just use the default settings
run weekly or monthly and clear all the other detritus as well