I have delevoped a small application in VB.net framework 3.5 using ODAC 12C Release 12.1.0.1.0. The target CPU is X86. The development system is Windows7, 64 bit. On an old XP machine with a number of old Oracle systems installed I installed the Xcopy code using "install.bat odp.net2 c:\OracleClient12 OraClient12Home1 true". I updated the PATH environment to include c:\OracleClient12. This runs perfectly. It finds the tnsnames.ora if located in the same directory as the program, or in c:\OracleClient12\networking\ADMIN. When I install the exact same setup on a VISTA system I get "Unable to load DLL 'OraOps12.dll' (0x8007007E). I have checked and there is only one version of Oracle.DataAccess.dll on the system and this is in C:\OracleClient12\odp.net\bin\2.x.It is Version 2.121.1.0. OraOps12.dll is in C:\OracleClient12\bin. This is the same as the working XP system and I believe this is correct. I am now totally lost on what to do next. Please,any ideas or suggestions as to what is wrong or how to find the problem would be welcomed.