Well, most of the software I came across was meant to prevent the problem from happening. Programs like "Clipboard Recovery" will not pull up old/deleted clipboard entries, it will just store everything you copy while it's running. The best program (and only program, as far as I know) to deal with this problem would be ManyClip, assuming it works with your computer. The program is rather old, but a number of websites still carry it, and should come up via a google search.
It's really a shame that more versions of manyclip, or programs like it, have never been developed.
Well, thanks again everyone.