Getting rid of unused Visual InterDev projects can be difficult if you try to do it the wrong way. If you go into the Web server’s file system and simply delete the files you may be unable to delete this file and folder:
The Web server’s grip on some files is so strong that even taking ownership won’t work. Rather than stopping the Web server to loosen the grip, make sure you remove old projects from within the Visual InterDev environment. Open the solution and right-click on the project name. From the context menu, click Delete Project. In the dialog box, choose whether you want to remove the local Web project, the master Web project or both. Don’t forget that you are also removing associated files.