recently I received a new laptop with windows 7 pro
oracle client 11.2.0 64bit version
I'm still using PL/SQL developer 7.0.3.1123
when I want to connect to a session;I get Initialization error:
"Could not load "C:\oracle\product\11.2.0\client_1\bin\oci.dll
...
LoadLibrary(C:\oracle\product\11.2.0\client_1\bin\oci.dll) returned 0"
------
and I can't login to the systems I need to monitor
connecting with:
>C:\oracle\product\11.2.0\client_1\bin\sqlplus.exe works OK
connection with TOAD works OK
what must be done to get PL/SQL developer working again???

You will need to install a 32 Bit Oracle11g or 12c Client. PL/SQL Developer is a 32 Bit application, so it cannot interface with a 64 Bit Oracle Client.

The 32 Bit Oracle Client can communicate with a 64 Bit Server, even on the same machine if necessary. The 32 Bit client can coexist with a 64 Bit Oracle installation when installed in separate Oracle Home directories.