Missing System.Windows Reference

I installed oracs beta on a vanilla Vista installation followed by the silverlight alpha addon.

When i created a new silverlight project, i found out that the System.windows package is missing.

The error message are as follows,

Error 1 The type or namespace name 'Windows' does not exist in the namespace 'System' (are you missing an assembly reference?) C:\Users\bgan\Documents\Visual Studio Codename Orcas\Projects\SilverlightProject1\SilverlightProject1\Page.xaml.cs 2 14 SilverlightProject1

I cannot find it anywhere on my system. Anyone has a pointer on where it is?

[614 byte] By [Bin.G] at [2008-1-3]