char exe[1024];
DWORD d;

GetWindowsDirectory(exe,sizeof(exe)-1);
strcat(exe, "\\SYSTEM32\\NOTEPAD.EXE");

hFile = CreateFile(exe, GENERIC_READ|GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
if(hFile!=INVALID_HANDLE_VALUE)
{
	d = GetFileSize(hFile, 0);
	hMapping = CreateFileMapping(hFile, 0, PAGE_READWRITE, 0, d, 0);
	mapping = MapViewOfFile(hMapping, FILE_MAP_READ|FILE_MAP_WRITE, 0, 0, d);

	// редактим блокнот в памяти

	UnmapViewOfFile(mapping);
	CloseHandle(hMapping);
	CloseHandle(hFile);
}