javaw.exe is used to run a Java server progress. If you run Java Web Server, you will see javaw.exe in Task Manager|Process.
You happened to click javaw.exe and I think this is what you meat by "harddisk running".

If you needs to run RMI service, you can either use javaw.exe or start java.exe.
Cay Horstmann argued that "start java.exe" is preferrable because one can kill the Java procecs using Control-C conveniently.