Grab your Office 2003 disc and copy the contents of it to: C:\XPCD\$OEM$\$1\install\Applications\Office2003\

The number of files may vary for different Office 2003 Editions, don't worry if its not the same as in the screenshot above.

Add these lines to your batch file:

ECHO.
ECHO Installing Office 2003
ECHO Please wait...
start /wait %systemdrive%\install\Applications\Office2003\PRO11.msi /QB

This will install the default components for Office 2003; which are Access, Excel, Frontpage, Outlook, Powerpoint, Publisher, Infopath and Word. You may want to do the Advanced version if you want full control over your Office 2003 Installation.