database = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source='c:\\Users\\test.xls';Extended Properties= \"Excel 8.0;HDR=Yes;IMEX=1\";");
The above connection string works using jet although i have to leave the excel file open for the time being as i get "could not decrypt file" error otherwise. I also had to save the file as a 97-03 excel xls file.