I installed Visual Studio 2010 Premium on my Windows 7 workstation. After loading a test C++ project, I noticed that it could not locate iostream. I took a look in C:\
The solution to this problem is as follows. It is based on the solution given in
http://connect.microsoft.com/VisualStudio/feedback/details/774158/re-installed-visual-studio-2010-and-c-standard-headers-are-missing
This solution may not be minimal, but it works for me. Hopefully others can confirm. The important difference here is that it is not just the HKEY_LOCAL_MACHINE from which the registry path must be deleted, as indicated in the link above.