We had the problem the we get this error, when we start the sqldeveloper.exe -> "unable to launch java virtual machine located..."
When I start the /sqldeveloper/bin/sqldeveloper.bat then the sqldeveloper works.
The first errormessage is "The program can't be startet, the MSVCR71.dll is missing on the computer."
The second errormessage is "Unable to launch the Java Virtual Machine Located at path: ..\..\jdk\jre\bin\client\jvm.dll"
But in the directory ..\..\jdk\jre\bin\client\ i can find the jvm.dll
At times it seems the DLL is not found by SQL Developer even though some version of it gets included with all the JDK versions:
1) Running on Win XP with JDK 1.7, SQL Developer wants the msvcr100.dll
2) Running on Win 7 with JDK 1.6, SQL Developer wants the msvcr71.dll
In these cases, copying the DLL into the ...\sqldeveloper\bin directory does the trick.
So by "it doesn't work" with just the instant client, you mean to say it still does not launch? But perhaps with a different error than the prior Java-related issue? I'll assume you have gotten past that.
Since SQL Developer only requires some type of Oracle client in certain cases, I'll guess there may be an issue with a left-over ORACLE_HOME environment variable or something similar. Why not try the following workaround discussed here: