provider error

I have an app that uses a Microsoft.Jet.OLEDB.3.51 provider. When I run the app on certain machines I get the following error: "ADO could not find the specified provider." (error 3706) I know that Microsoft.Jet.OLEDB.3.51 is installed on the machine because I downloaded it from Microsoft myself. Does anyone know why this is happening?
Thanks

Jose

Register the dll you down loaded by using regsvr32.exe