If you upgrade your Java SDK, the NetBeans IDE may give you the following error message (Invalid jdkhome specified) at startup:

Cannot find java.exe in specified jdkhome.
Neither C:\Program Files\Java\jdk1.6.0_10\jre\bin\java.exe 
    nor C:\Program Files\Java\jdk1.6.0_10\bin\java.exe exists.
Do you want to try to use default version?

This can be corrected by manually editing the netbeans.conf file found under:

%PROGRAMFILES%\NetBeans 6.5\etc

Replace the line netbeans_jdkhome with the correct path information. Alternatively, you can comment out the line entirely with # and NetBeans will use your default JDK, through JAVA_HOME.