Sure it was supported only on 32bits - there was no 64bit Windows at the time they created it. However this seems to be a problem of MS JVM installation. If you manage to install it properly (which I doubt) on Windows 64bit you should be able to run it fine. Wait till Q1 2008 when pure Java version of client for SD 4.5 shoudl be out. That should run on anything that supports Java and that includes Windows 64bit versions.