hier ein auszug ausm code:

char *LoadFileToObj(char* file, HWND toshow) 
{ 
	HANDLE hf;
	hf = CreateFile(file, GENERIC_READ, FILE_SHARE_READ, (LPSECURITY_ATTRIBUTES) NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, (HANDLE) NULL);
	unsigned long nRead = GetFileSize(hf,NULL);
	char *lpbuffer = new char[nRead];
	unsigned long nBytesRead;
	lpbuffer[nRead]=0;
	ReadFile(hf,lpbuffer,nRead,&nBytesRead, NULL);
	SetWindowText(toshow, file);
	return lpbuffer;
}
void SaveToFile(char *pFilename, char *pBuffer, int nSize) 
{
	HANDLE hf;
	hf = CreateFile(pFilename, GENERIC_WRITE, FILE_SHARE_READ, (LPSECURITY_ATTRIBUTES) NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, (HANDLE) NULL);
	unsigned long nBytesRead;
	WriteFile(hf , pBuffer, nSize, &nBytesRead, NULL);
}
inline int GetEditTextLength(HWND hWnd) 
{ 
  return SendMessage(hWnd, WM_GETTEXTLENGTH, 0, 0)+1; 
}
void OpenOrSaveDlg(bool mode, HWND hFileWindow, HWND hContentWindow, HWND hwnd)
{
	if(mode == TRUE) 
	{
		OPENFILENAME ofn;       // common dialog box structure
		char szFile[260];       // buffer for file name<
		// Los Gehts (MSDN krams)
		//Memory leeren:
		ZeroMemory(&ofn, sizeof(ofn));
		//Grösse, Owner, File...
		ofn.lStructSize = sizeof(ofn);
		ofn.hwndOwner = hwnd;
		ofn.lpstrFile = szFile;
		//
		// Set lpstrFile[0] to '\0' so that GetOpenFileName does not 
		// use the contents of szFile to initialize itself.
		//
		//Anm,: ???
		ofn.lpstrFile[0] = '\0';
		ofn.nMaxFile = sizeof(szFile);
		ofn.lpstrFilter = "All\0*.*\0Text\0*.TXT\0";
		ofn.nFilterIndex = 1;
		ofn.lpstrFileTitle = NULL;
		ofn.nMaxFileTitle = 0;
		ofn.lpstrInitialDir = NULL;
		ofn.Flags = OFN_OVERWRITEPROMPT;
		if (GetSaveFileName(&ofn)==TRUE) 
		{
			char *lpBuffer = new char[GetEditTextLength(hContentWindow)];
			GetWindowText(hContentWindow, lpBuffer, GetEditTextLength(hContentWindow));
			SaveToFile(ofn.lpstrFile, lpBuffer, GetEditTextLength(hContentWindow));
		}
	}
	if(mode == FALSE) 
	{
		OPENFILENAME ofn2;
		char szFile[260];      
		ZeroMemory(&ofn2, sizeof(ofn2));
		ofn2.lStructSize = sizeof(ofn2);
		ofn2.hwndOwner = hwnd;
		ofn2.lpstrFile = szFile;
		ofn2.lpstrFile[0] = '\0';
		ofn2.nMaxFile = sizeof(szFile);
		ofn2.lpstrFilter = "All\0*.*\0Text\0*.TXT\0";
		ofn2.nFilterIndex = 1;
		ofn2.lpstrFileTitle = NULL;
		ofn2.nMaxFileTitle = 0;
		ofn2.lpstrInitialDir = NULL;
		ofn2.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
		if (GetOpenFileName(&ofn2)==TRUE) 
		{
			SetWindowText(hContentWindow, LoadFileToObj(ofn2.lpstrFile, hFileWindow));
		}
	}
}

Man lese die MSDN bezüglich CreateFile etwas genauer...