http://msmvps.com/blogs/carlosq/archive/2008/08/10/more-one-prb-quot-could-not-copy-temporary-files-to-the-output-directory-quot-when-running-add-in-project.aspxThree years ago I wrote the article PRB: &#39;Could not copy temporary files to the output directory&#39; error building Visual Studio .NET add-in explaining the common cause for that error when running an add-in project. There is a second cause thatenCommunityServer 2008.5 SP2 (Build: 40407.4157)http://msmvps.com/blogs/carlosq/archive/2008/08/10/more-one-prb-quot-could-not-copy-temporary-files-to-the-output-directory-quot-when-running-add-in-project.aspx#1720255Wed, 02 Sep 2009 17:12:22 GMTd67277c4-116b-43f1-b688-e9ef184ea916:1720255cguillemette<p>Never thought of using ProcessExplorer. What I do is open the task manager and move the mouse over the visible IDE. Then I close the the instance of devenv.exe that gets no CPU cycles. Hope this helps.</p> <div style="clear:both;"></div><img src="http://msmvps.com/aggbug.aspx?PostID=1720255" width="1" height="1">