(This didnt fit in a Comment box)
You need at least one driver. The oracle driver is best but Microsoft Driver will work too.
Lets first try to make a connection string. Right click on your desktop and the create a new .txt file.
Now rename your textfile to something.udl
Double click on the udl file. Go to "Provider" and select Microsoft OLEDB Provider for Oracle. Then click on next. In the server name field you fill in your TNS name. Then username and password and put a V inside "Allow saving password" (we will need this) And click on test connection. Make sure this works.
If it works then click on OK. Now open the UDL file with a text editor. You will see something similar to:
[oledb]
; Everything after this line is an OLE DB initstring
Provider=MSDAORA.1;Password=yourpw;User ID=youruser;Data Source=yourTNS;Persist Security Info=True
Copy this part into your connection string:
Provider=MSDAORA.1;Password=yourpw;User ID=youruser;Data Source=yourTNS
Now your connection string should look like:
Conn = "Provider=MSDAORA.1;Password=yourpw;User ID=youruser;Data Source=yourTNS"
I hope this works.