What causes Windows 7 to give “Provider cannot be found. It may not be properly installed” (identical code works fine on Windows xp)

Question

Windows 7 produces the following error message on 'localhost/xxxx' (identical code used to work on Windows 7 and still works on Windows xp)

"Provider cannot be found. It may not be properly installed" 

... Provider=Microsoft.Jet.OLEDB.4.0

As I recall Windows 7 worked in the past. In any case, what causes the above error message in Windows 7?