How much have you Googled this? It would be helpful to know what troubleshooting you've tried. I see that you tried installing ODAC, but from glancing around on the interwebs, it looks like other people have also had to make an entry in the tnsnames.ora file. See
here on the msdn forums. And are you sure you need the 32-bit version of ODAC?
Here's another suggestion as well regarding registering the installed provider through command prompt.
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Dave Morris
3Ci @ Southern Company
Atlanta, GA
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Dave Morris, 3Ci at Southern Company