Make sure that all instances of VS.NET are closed.

Then type "regedit" in the Run window (Start>Run) and hit enter.

Go to the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\7.1\ProjectMRUList
(or perhaps 8.0 if 2005) and delete this key.

Now when you run the VS.NET IDE, you will see a blank 'Start Page'.