In CRM 3.0 it was relatively easy to hide one of the built-in system views - all you had to do was share the view with an empty team, which converted the view to a userquery entity. However, CRM 4.0 does not support this.
There is an alternative route, but it required plug-in coding. Rather than have to write code for each deployment, I created a standard plug-in that can be used to hide any views, based on some XML configuration. The source code and compiled code is available on the MSDN Code Gallery, along with a sample configuration file.