The Recent Docs menu can be easily disabled by editing the Registry.
To do this go to the following Key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

Now in the right pane,
create a new DWORD value by the name: NoRecentDocsMenu and set it's value to 1.
Restart Explorer to save the changes.
You can also clear the RUN MRU history.
All the listings are stored in the key:

HKEY_USERS\.Default\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMR

You can delete individual listings or the entire listing.
To delete History of Find listings go to:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Doc

Find Spec MRU and delete