DWORD cchCurDir
LPSTR lpszCurDir;
TCHAR tchBuffer[MAX_PATH];

lpszCurDir = tchBuffer;

DWORD OK = GetCurrentDirectory(cchCurDir,lpszCurDir);

CString s(lpszCurDir);
s = s + "\\index.htm";

ShellExecute(m_hWnd,"open",s,NULL,NULL,SW_SHOWNORMAL);