no new window for HTML pages in Visual Studio 2010?

I've tried this on two different machines now on Windows 7 and it appears that the Window > New Window menu command is not available in Visual Studio 2010. It 开发者_如何转开发doesn't work for HTML, .aspx, and .js files, but does work for .css, .cs, and .xaml files. Has anyone else noticed this or knows why this is?

(I have the productivity power tools extension installed)

I found a registry entry at [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\10.0\Languages\Language Services\HTML] or [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\VisualStudio\10.0\Languages\Language Services\HTML] for 64 bit machines called "Single Code Window Only" I deleted it and the menu command showed up! Then I made a new window, and it was completely blank. I checked with Visual Studio 8 and found the same thing. Apparently they have not implemented "new window" for some file types. Apparently they had started to implement it for Visual Basic Files, but had it disabled because it hadn't been thoroughly tested yet ( http://msmvps.com/blogs/deborahk/archive/2010/05/17/visual-studio-window-new-window.aspx ).