Check [url][/url] and look for /Gr /Gz or /Gd compiler options.

How about this:
highest = 0;
lowest = 0;

for(int month = 0; month < NUM_MONTHS; month++)
if ( values[month] > values[highest] )
highest = month;
if ( values[month] < values[lowest] )
lowest = month;
//Display total rainfall for year, monthly average, highest and lowest months
cout << endl << endl
<< "The total rainfall for the year is: " << total << " inches" << endl
<< "The average monthly rainfall is: " << average << " inches" << endl
<< "The month with the highest rainfall is: " << months[highest] << endl
<< "The month with the lowest rainfall is: " << months[lowest] << endl;

windows.h is not a library. It a header. There are numerous Win32 libs behind it (kernel32.lib;user32.lib;gdi32.lib;winspool.lib;comdlg32.lib;advapi32.lib;shell32.lib;ole32.lib;oleaut32.lib;uuid.lib to name a few). Anyhow, I would not recommend doing bare bone win32 as it is too MS platform specific. Contemporary GUI libraries abstract an underlying platform. Take a look at Qt [URL=""]here[/URL]. It's one of the most popular cross platform C++ libraries and its an Open Source and free like in beer.

Compiler (C/C++) advanced setting -> Calling convention should be the same for all files in your VS project. __fastcall (/Gr) is preferable for "Release" builds.