You mean the TypedURLs list from the address bar, right?
Those are in a TypedURLs key in the registry. This article explains the
TypedURLs history:
157729 - How to Clear the History Entries in Internet Explorer: http://support.microsoft.com/default.aspx?scid=kb;en-us;Q157729
Removing some or all entries is an easy registry edit.
If you type URLs in via File> Open, instead of the address bar, they aren't
saved in the TypedURLs key and you can keep a select few URLs in the
drop-down list.