I installed VS2008 on a system that also has SQL Server 2005 installed. The SQL Server setup automatically installs a special copy of VS2005. When installing the GAX, it asks whether to install GAX for VS2005 or VS Codename "Orcas". I chose the "Orcas" option.
After installing the GAX, I then installed the GAT. It ran to completion without prompting for a target environment. When I then open VS2008, there is no guidance package manager and there are no project templates for creating a guidance package.
Examining the package load analyzer shows that there was a problem loading the recipe framework. It appears there are some dependent assemblies missing. I have not been able to determine which ones are missing.
Examining the VS2008 installation folders, there are no project or item templates related to GAX/GAT.