When you click on \[Start\] and then on Run.. you can either type your command or select a previously typed command from the dropdown list. If you're like me, your dropdown list is a mess. This list is stored as up to 26 value entries in the registry at:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU

Additionally, the sequence of this list is stored in the value MRUlist. Alter entries "a" through ... and delete the extra entries (each entry must end with a "\1"). The MRUlist should be edited to reflect the desired sequence and should not contain letters for the deleted entries. It is best to leave no gaps in the letter sequence. You must reboot for the changes to take effect.

OR

Alter entry "a", delete "b" through "z". Change MRUlist to a. After rebooting, type the commands into the run dialog in the reverse order you wish them stored. You can also drag executable files (even documents with associations) from Explorer.