Well, Firstly, the slashes should be the other way.... I know in later versions of windows it understands both, but if you run it on a box that is earlier versions of window, most likely ME or 98, it will get pretty upset with you. The keyword to check if a file exists, is "dir", and you can use it to check for wildcards as such:
Dim Fname As String
Fname = Dir("c:\program\*.id", vbNormal)
While Fname <> ""
Fname = Dir
That will only msgbox (popup) the names of all the files ending in .id in the c:\program directory.... if you want to Search The Entire Hard Drive, you can do that too... let me know if you have any further questions.