to register system level association , we need to write to HKLM registry branch, which java web start won't have permission to do so on Vista.

Problem exists in older JRE as well, e.g I tested on 6.0

com.sun.deploy.association.RegisterFailedException: Key SOFTWARE\Classes\MIME\Da
tabase\Content Type\application/x-dmt creation error!
        at com.sun.deploy.association.utility.WinRegistryUtil.regCreateKeyEx(Unk
nown Source)
        at com.sun.deploy.association.utility.WinRegistryUtil.addMimeType(Unknow
n Source)
        at com.sun.deploy.association.utility.WinAppAssociationWriter.registerAs
sociation(Unknown Source)
        at com.sun.deploy.association.AssociationService.registerSystemAssociati
on(Unknown Source)
        at com.sun.javaws.WinInstallHandler.registerAssociationInternal(Unknown
Source)
        at com.sun.javaws.LocalInstallHandler.registerAssociation(Unknown Source
)
        at com.sun.javaws.LocalInstallHandler.createAssociations(Unknown Source)
        at com.sun.javaws.LocalInstallHandler.performIntegration(Unknown Source)
        at com.sun.javaws.LocalInstallHandler.install(Unknown Source)
        at com.sun.javaws.Launcher.notifyLocalInstallHandler(Unknown Source)
        at com.sun.javaws.Launcher.prepareLaunchFile(Unknown Source)
        at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
        at com.sun.javaws.Launcher.launch(Unknown Source)
        at com.sun.javaws.Main.launchApp(Unknown Source)
        at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
        at com.sun.javaws.Main$1.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)

we probably need to use jbroker to create the keys