How do include paths work in Visual Studio?

Visual Studio drives me crazy and I am suspecting I am doing something wrong.

This is what I do: I installed Visual Studio (Pro '08) a long time ago, I installed the Windows SDK (Win 7 x64), someone emails me a project, it fails to build.

Invariably, it can not find windows.h. While it is easy enough to include C:\Program Files\Microsoft SDKs\Windows\v7.0\Include in the project settings of every single project, I feel that this may not be the proper way to do it. Is there a way to somehow make Visual Studio globally aware of these files?
I also tried to include the above directory in the path variable but that didn't change anything.

Also, it will randomly find windows.h but not winresrc.h in the same directory.

Edit:
It was a problem with my machine. Somehow, Visual Studio thought that my Windows SDK was in the wrong place. See accepted answer and comments for the fix.

@RichieHindle solution is now deprecated as of Visual Studio 2012. As the VS studio prompt now states:

> VC++ Directories are now available as a user property sheet that is added by default to all projects.

To set an include path you now must right-click a project and go to:

Properties/VC++ Directories/General/Include Directories

Screenshot:

This answer only applies to ancient versions of Visual Studio - see the more recent answers for modern versions.

You can set Visual Studio's global include path here:

Tools / Options / Projects and Solutions / VC++ Directories / Include files

To resume the working solutions in VisualStudio 2013 and 2015 too:

Add an include-path to the current project only

In Solution Explorer (a palette-window of the VisualStudio-mainwindow), open the shortcut menu for the project and choose Properties, and then in the left pane of the Property Pages dialog box, expand Configuration Properties and select VC++ Directories. Additional include- or lib-paths are specifyable there.

Its the what Stackunderflow and user1741137 say in the answers above. Its the what Microsoft explains in MSDN too.

Add an include-path to every new project automatically

Its the question, what Jay Elston is asking in a comment above and what is a very obvious and burning question in my eyes, what seems to be nonanswered here yet.

There exist regular ways to do it in VisualStudio (see CurlyBrace.com), what in my experience are not working properly. In the sense, that it works only once, and thereafter, it is no more expandable and nomore removable. The approach of Steve Wilkinson in another close related thread of StackOverflow, editing the Microsoft-Factory-XML-file in the ‘program files’ - directory is probably a risky hack, as it isnt expected by Microsoft to meet there something foreign. The effect is potentally unpredictable. Well, I like rather to judge it risky not much, but anyway the best way to make VisualStudio work incomprehensible at least for someone else.

The what is working fine compared to, is the editing the corresponding User-XML-file:

> C:\Users\UserName\AppData\Local\Microsoft\MSBuild\v4.0\Microsoft.Cpp.Win32.user.props

or/and

> C:\Users\UserName\AppData\Local\Microsoft\MSBuild\v4.0\Microsoft.Cpp.x64.user.props

For example:

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <ImportGroup Label="PropertySheets">
  </ImportGroup>
  <PropertyGroup Label="UserMacros" />
  <PropertyGroup>
    <IncludePath>C:\any-name\include;$(IncludePath)</IncludePath>
    <LibraryPath>C:\any-name\lib;$(LibraryPath)</LibraryPath>
  </PropertyGroup>
  <ItemDefinitionGroup />
  <ItemGroup />
</Project>

Where the directory ‘C:\any-name\include’ will get prepended to the present include-path and the directory ‘C:\any-name\lib’ to the library-path. Here, we can edit it ago in an extending and removing sense and remove it all, removing thewhole content of the tag .

Its the what makes VisualStudio itself, doing it in the regular way what CurlyBrace describes. As said, it isnt editable in the CurlyBrace-way thereafter nomore, but in the XML-editing-way it is.

For more insight, see Brian Tyler@MSDN-Blog 2009, what is admittedly not very fresh, but always the what Microsoft is linking to.

To use Windows SDK successfully you need not only make include files available to your projects but also library files and executables (tools). To set all these directories you should use WinSDK Configuration Tool.

If you are only trying to change the include paths for a project and not for all solutions then in Visual Studio 2008 do this: Right-click on the name of the project in the Solution Navigator. From the popup menu select Properties. In the property pages dialog select Configuration Properties->C/C++/General. Click in the text box next to the "Additional Include Files" label and browse for the appropriate directory. Select OK.

What annoys me is that some of the answers to the original question asked do not apply to the version of Visual Studio that was mentioned.

This answer will be useful for those who use a non-standard IDE (i.e. Qt Creator).

There are at least two non-intrusive ways to pass additional include paths to Visual Studio's cl.exe via environment variables:

• Set INCLUDE environment variable to ;-separated list of all include paths. It overrides all includes, inclusive standard library ones. Not recommended.
• Set CL environment variable to the following value: /I C:\Lib\VulkanMemoryAllocator\src /I C:\Lib\gli /I C:\Lib\gli\external, where each argument of /I key is additional include path.

I successfully use the last one.

You need to make sure and have the following:

#include <windows.h>

and not this:

#include "windows.h"

If that's not the problem, then check RichieHindle's response.