While that error is supposed to mean that the driver/provider isn't installed, it usually means is that something is wrong with your connection string. Check www.connectionstrings.com to see valid examples, you just need to change file names etc.

Also, is OleDB the usual way to read data from Excel?
It is one of the usual ways... the other is to automate Excel (as shown in the Office Development FAQs), but that requires Excel to be installed.