I had the same problem but with the Oracle 9i client. However the MSDN
information listed in this thread at http://tinyurl.com/5u5d9 does not
address Oracle 9i. Nevertheless, I was able to resolve it by adapting
the registry values to reflect 9i.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI ]
"OracleXaLib"="oraclient9.dll"
"OracleSqlLib"="orasql9.dll"
"OracleOciLib"="oci.dll"

I had the same problem but with the Oracle 9i client. However the MSDN
information listed in this thread at http://tinyurl.com/5u5d9 does not
address Oracle 9i. Nevertheless, I was able to resolve it by adapting
the registry values to reflect 9i.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI ]
"OracleXaLib"="oraclient9.dll"
"OracleSqlLib"="orasql9.dll"
"OracleOciLib"="oci.dll"

http://tinyurl.com/5u5d9

This works with Oracle 9i client as well; however, the following
changes need to be made to the registry.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI ]
"OracleXaLib"="oraclient9.dll"
"OracleSqlLib"="orasql9.dll"
"OracleOciLib"="oci.dll"

http://tinyurl.com/5u5d9

This works with Oracle 9i client as well; however, the following
changes need to be made to the registry.

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSDTC\MTxOCI ]
"OracleXaLib"="oraclient9.dll"
"OracleSqlLib"="orasql9.dll"
"OracleOciLib"="oci.dll"