JDK installation defaults the classpath to the JRE libs? (tools.jar unavailable)

[Abuse]

I'm specifically dealing with a Windows installation of jdk1.5.0_08 here.

When installing the JDK, the classpath appears to be defaulting to the JRE libs not the JDK libs, meaning tools.jar is unavailable.
This seems rather illogical behaviour.
There also doesn't seem a neat way of selecting which libs folder is used for the default classpath.
( I presume it pulls the default classpath from the registry keys in "HKEY_LOCAL_MACHINE\Software\JavaSoft\" )

I'd have expected the Java 'Control Panel' entry to allow you to specify this kind of stuff.
However, this has always seemed incomplete. (you can view the runtime settings for applets & webstart, but can only modify the webstart settings)
Which of these 2 controls the default classpath used when java is invoked on the command-line? or is it neither!

btw, I'm purposely ignoring the CLASSPATH environment variable. I want to change the underlying default classpath, not override it.

Am I missing something, or is this simply not possible without messing around with the registry? (which itself is no fun, as the full absolute path is duplicated about 20 times in different keys).

[Abuse]

Feel free to move this to an appropriate forum; though we don't realy have a "general java programming" forum