Minecraft is a game developed in Java, so it needs JRE (Java Runtime Environment) if you want to play the "desktop" version, while the "browser" version needs only the java plugin for the browser.
Ok, my friend has installed Java 6.29, but... the system doesn't know the right path and Minecraft doesn't found the Java directory:
"Error: the registry refers to a nonexistent Java Runtime Environment installation or the runtime is corrupted."
|Write java -version in the prompt (Run>cmd) for the Java version installed.|
An "Error: could not open c:\Program Files\Java\jre6\lib\amd64\jvn.cfg" with a incorrect path...
The directory amd64 doesn't exists and the java installation is for an Intel cpu.
Java removing, java re-installing, system registry cleaning ... doesn't work.
Searching for this path in some registry key ... nothing
Setting a "path" variable in the system environment variables... nothing
The solution is there!
-Download the JavaMSIFix.exe that fixes the registry (where? I don't know, I destroyed my F3 button searching in the registry)
-Install the 1.6.x (x86,x64) version of Java