When installing a new JDK on a windows slave, there appears to be a quoting issue with the arguments passed to the installer. From the console output:

[jdk-1.6.0_17] $ C:\hudson-tmp\tools\jdk-1.6.0_17\jdk.exe /s '/v/qn REBOOT=Suppress INSTALLDIR=\"C:\hudson-tmp\tools\jdk-1.6.0_17\" /L \"C:\hudson-tmp\tools\jdk-1.6.0_17\jdk.exe.install.log\"'

Notice how the /s is outside of the single quotes where the rest of the options are (/v/qn ...). Comments in the WINDOWS case of JDKInstaller.java#install seem to indicate that the options to the installer should be passed as one string. However, the code adds two strings - one for /s and another for the rest of the options.

The result is that the jdk fails to install. However, executing C:\hudson-tmp\tools\jdk-1.6.0_17\jdk.exe /s /v/qn REBOOT=Suppress INSTALLDIR=\"C:\hudson-tmp\tools\jdk-1.6.0_17\" /L \"C:\hudson-tmp\tools\jdk-1.6.0_17\jdk.exe.install.log\" on a command prompt successfully installs the JDK.