Here are a couple handy links describing how to remove items from the Recent Projects list on the Visual Studio start page. Basically, in versions prior to VS2010, it’s a registry hack (I’ve read that VS2010 provides a way to do this within the IDE, but I haven’t played with 2010 yet so I can’t attest to that myself) [Update: it does – right click the item and select ‘Remove’].
http://mvantzet.wordpress.com/2009/09/15/remove-recent-projects-from-visual-studio-2008/
When I removed some items from my version of VS 2008, I found that I also needed to rename the remaining registry keys so that there were no gaps in the order (ie, File1, File2, etc with no gaps)
TechKnowSolve Blog 