I recently re-installed the ADS XScale 4.2 SDK after having removed it for a while to save disk space. The 4.2 platform is not listed in the platform manager when I use any of the remote tools, nor is it listed when I create a new project.
I'm actually surprised it showed in the first place. Studio 05 does not support debugging on CE 4.2 devices (though for managed code you can get it to work with a 5.0 SDK and manual deployment of CF 2.0 SP1)