Right click any unwanted URL and click Delete.
To clear all drop down URLs including Typed URLs, open notepad and copy/paste the below as typedURLs.inf :
; To execute this file: in Explorer - right-click (this file)
; Select: "Install" from the menu.
[version]
signature="$CHICAGO$"
[DefaultInstall]
DelReg=DelTemps
AddReg=AddTemps
[DelTemps]
HKCU,"Software\Microsoft\Internet Explorer\TypedURLs"
; now let's recreate the entry, to prevent the need to reboot.
[AddTemps]
HKCU,"Software\Microsoft\Internet Explorer\TypedURLs"
--------------------------- end copy/paste above this line
Right-click on the saved file and choose Install.