You should let us know the compiler for better response but you should specify the path of the files correctly in the directory options.
Unable to open include file usually means (a) the header files aren't present or (b) the environment is not setup correctly. What OS are you using? Do the files exist? If you're using Windows, try dir/s c:\iostream.h and repeat for each drive (so if you also have a hard drive on D: replace C: with D: to search that drive. Or use the Windows search facility to search "All local drives". If you're using a Unix clone try find / -name iostream.h -print. If the files exist then you probably need to set an environment variable, or include the path in the project file. If the files don't exist then you need to (a) remove the references to those headers or (b) install them one way or another.
