Can’t find PROI11.MSI

I am trying to apply SP 2 to an install of Office 2003 pro (installed before I got here from a CD I can not identify). When this update begins, it asks for the Office 2003 Professional CD. When I insert it, it tells me it can not find a proper PROI11>MSI. On the CDs I have, there is only PRO11.MSI (no “I”).

Does anyone know where I can get my hands on a CD with this MSI file?