Update Failure with Office XP, also unable to Replace/Repair.

[BlueEagle]

Right, in order of how I tried to install SP3 to MSOfficeXP Small Business edition:

First via the MS update site I got this message:

"Error! Unable to check for updates on this computer Help

"The Office Update site is unable to check for updates on this computer. This may be happening because of one of the following reasons:

You do not have administrative privileges for this computer.
There is a network problem and the detection catalogue used by the Office Update site failed to download. Go back to the Downloads home page and try running detection again.
Windows Installer patch files (.MSP files) from previously applied Office updates are missing from the \Windows\Installer hidden directory on your computer. MSP files are stored on your computer after update installation completes because they need to be referenced for future update operations. If the files are missing you will not be able to apply Office updates. You may also be unable to un-install Office products as a result of the same problem. Please contact Microsoft Product Support Services for assistance.
You installed Office updates in the past and then upgraded from Windows Installer version 1.0 to Windows Installer version 1.1. For more information see the KB article Windows Installer May Prompt for Install Source if Unavailable."

Well it's definitely neither of the first two.

Then I downloaded the full SP3, 57MB, OfficeXPSp3-kb832671-fullfile-enu.exe but when I try to install that I get:

“Office Hotfix Installer Encountered a problem. We are sorry” etc. etc.

and the data says:

ProdCode: x ProdVer: x Action: HotfixDetection NPUErr.

Err Num: 1635 Err: 0 {DA256408-A2E7-41A5-8AD6-62ACB86A0FD7}

Err1: Normal Patch.cpp Err2: 139
Which is all Greek to me but does suggest it may be an installer problem?

Finally I put in the CD for MS OfficeXP Small Business in order to either re-install it or run Replace and Repair and get this message:
"This package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer Patch Package"

A strange message considering I am trying to run Set-Up from the original CD.

Have been to the MS support site but didn't immediately come up with anything, however will go back now as I have a bit more time.

Would appreciate any thoughts and ideas. Many thanks.