Setting "Type of File" when using WINDOWS Explorer to perform a se

In my Windows Explorer search feature, the "type of file" drop down selection
is set to 'null/blank' which apparently equates to "all file type" - which is
a GOOD thing. When the search is finished, the top value in the drop-down
list (3GPP) is selected - thus restricting subsequent searchs to that file
type. From this point forward, a selection MUST be made, but there is no
selection for "all file types". Restarting Explorer is the only way to reset
this field

Can the file type be reset to "all files" or NULL or blank w/o having to
restart Explorer? Is there some way to add "all files" to the drop-down list?