There is a known issue with the Platformer starter kit not appearing in any editions of Visual Studio 2008 installed after you install XNA Game Studio 3.0. Repairing XNA Game Studio 3.0 does not fix this issue. If you run into this issue, you will need to use the following steps to work around it:
- Go to %ProgramFiles%\Microsoft XNA\XNA Game Studio\v3.0\Setup, right-click on platformer.msi and choose to uninstall it
- Go to Add/Remove Programs and choose to repair Microsoft XNA Game Studio 3.0.
Please let us know if that does not solve this issue for you.