Just playing around. I'm on Vista Home Premium 64 bit SP1 at the moment. I went into Start Menu and right clicked on Recent Items. Then I went to Send To and chose Desktop. Now I had a shortcut on the desktop. I dragged it onto a File Open dialog and renamed it Recent Items. Then I deleted the shortcut on the Desktop. I'l have to watch it for awhile to see if it get updated.
Might be worth a try.
edit: seems to be working. I opened a text file and then looked in File Open and File Save As dialogs. Recent Items is there and that text file is listed. I'm glad you asked. I may want to use this myself.
edit2: I just did the same thing in Windows 7 32 bit. If it doesn't show Recent Items in the Start Menu panel, right click TaskBar, select Properties, then Start Menu, then Customize. Once it shows in the Start Menu panel then you can do the SendTo Desktop trick.