Office XP SP3 update: problems without install CD

The SP3 package is available here on:
http://software.techrepublic.com.com/download.aspx?docid=196153
When installing a dialogue asks for the OfficeXP CDrom in order to execute PRO.MSI

But our PC comes from an external agency as part of an agreed funding package - we do not have the original installation CD's. So the installation stops reporting a fatal error and SP3 cannot be installed.

Now we can't open any OfficeXP applications on this computer without being asked for PRO.MSI and the software suite is effectively broken until a copy of this file can be found.

For the benefit for anyone else who mines the internet to tackle this problem, I hope that in response to this, contributors can deposit solutions for:

1. Undoing the update so that we can continue to use Office on this computer until an install CD or a copy of the correct file "PRO.MSI" can be located. System Restore had no impact. As a last resort (before removing Office altogether and using OpenOffice instead) I might try to remove update KB832671 - but I fear this might make things much much worse and consume too much time.

2. Completing the update while getting around the requirement to have PRO.MSI.

Finally: Let's all moan and gripe at this Microsoftary nonsense that overcomplicates simple tasks, enthralls na?ve users with configuration issues and probably causes more IT downtime than floods, fires and wars - put together!