Just what the title says. Likewise, I cannot include Windows.h or use its data types.

- I am using Microsoft Visual Studios 2010 in combination with DirectX9.
- I have added the Lib/Include files to my Include directory, the x86 folder to my Lib directory, and the DxErr folder to my Source directory across all configurations
- I do not have "Ignore Standard Include Paths" ticked across all configurations
- My SDK is from June 2010.
- I have included the following in my Linker Input across all configurations

• d3d9.lib
  
• d3dx9.lib
  
• DxErr.lib
  
• dxguid.lib
  
• dsound.lib
  
• winmm.lib
  
• dinput8.lib
  

- I am manipulating a Win32 project that started empty.
- None of my other DirectX programs are giving me this problem

Instead of using completely original files, I attempted to use existing source and header files from my other projects. Would that cause something like this? It doesn't seem very likely...

What is your exact error message?

Well, I haven't put together all the sources files together in a way that fits yet. It's that when I mouse over the preprocessor directives, there's a red line underneath and it says what it says in the title: Cannot open source file 'time.h', Cannot open source file 'stdio.h' etc. Those are pretty standard things, right? Like, I wouldn't be able to miss those if I tried?

Are the standard library folders in the include directories in the project settings? Also, if you're using C++ give cstdio and ctime a try instead.

Well, I haven't put together all the sources files together in a way that fits yet. It's that when I mouse over the preprocessor directives, there's a red line underneath and it says what it says in the title: Cannot open source file 'time.h', Cannot open source file 'stdio.h' etc. Those are pretty standard things, right? Like, I wouldn't be able to miss those if I tried?

If by this you mean you haven't actually compiled anything yet, well...do so. I've had red squiggly lines many times that were totally bogus; there was nothing wrong.