Use the shellExecute function. There's plenty of documentation on it in the MSDN. I copied this from a piece of one of my functions which wouldn't actually open notepad, it opens from a filename, in which case if it was a file with a *.txt extension it would open up the default application for that extension, in the case of .txt, Notepad. Hope this helps!
int iReturn = (int) ShellExecute(NULL, "open", "c:\\windows\\system32\\notepad.exe", NULL, NULL, SW_SHOWNORMAL);
// If ShellExecute returns an error code, let the user know.
if (iReturn <= 32)
{
MessageBox ("Cannot open file. File may have been moved or deleted.", "Error!", MB_OK | MB_ICONEXCLAMATION) ;
}