It's in the registry, give me a while
I'm not positive this is the one, but backup the registry key before making the change.
Open regedit and navigate to :
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\AutoComplete
In the right hand pane create a new String Value and name it AutoSuggest ad give it a value of yes.
also create a new String value named Append Completion and give it a value of yes
Reboot you compyuyer.
If a;ll these fail, open Internet options and click the Advanced tab, then the Reset button.