Add the Oracle client path at the front of the PATH Environmental Variables.
To do this please follow the steps below:
1. Go to your My Computer Icon, right click.
2. Select Properties | Advanced | Environmental Variables.
3. Under the System Variables section, find the PATH.
PATH should begin with the path to the intended client's bin folder, which holds the client's dlls. If this is not already found in the front, edit PATH and add the client's bin path to the front of the string.