I'm guessing you are using ADO, and am also guessing that you are distributing MDAC 2.1, which does not include the Jet OLEDB 3.51 provider.

Distribute MDAC 2.0 instead, you can get it at
http://www.integrade.com/downloads/mdac.html

or off your visual studio cd

MDAC 2.0 includes the driver for Jet 3.51