In Visual Studio, if we want to delete the recent project history, we have to delete thru Registry only, there is no direct option to delete. Already we discussed this on, one of my old post, Titled as “How to Clear Visual Studio 2005 or 2008 Recent project List?”
Deleting thru Regitry is not a good idea, we shouldn't do this, if necessary, we have to access the registry very carefully.
To avoid this, Now "MRU Cleaner" VS 2005/2008 Add-in tool is available to clear recent project or recent file from Visual Studio IDE
This version includes the ability to now clear your Most Recently Used Files list in addition to the already-existing ability to clear your Projects list.
You can download this from Download MRU Cleaner
After install this, you can find the menu "Clear Recent Items.."
see the Screenshot below: