When launching HOBOware I was informed that there is no Java Virtual Machine installed, and was directed to the Onset web site for help installing a JVM.
Note first that the preferred JVM is version 5, also known as version 1.5. There are two sources of the JVM, also known as the Java Runtime Environment (JRE), that you can use:
The simplest might be the JRE installer that is re-distributed on the HOBOware CD - using Windows Explorer, look in the Java-JRE folder on the CD. Double-click the executable file named something like jre-1_5_0_13-windows-i586-p.exe and follow the instructions.