Thanks Marco :-)

I reinstalled the 10g client and set the field above as stated, but still get:

Initialization error
Could not load "D:\oracle\product\10.2.0\client_1\bin\oci.dll"

OCIDLL forced to D:\oracle\product\10.2.0\client_1\bin\oci.dll
LoadLibrary(D:\oracle\product\10.2.0\client_1\bin\oci.dll) returned 0

I didn't get any errors during the 10g client install. Any other ideas?

Thanks!