Thanks, I had found that link also, followed it and eventually found the the key
HKEY_LOCAL_MACHINE, SYSTEM, CurrentControlSet, Services, MSIServer
was totally missing from the registry. I then imported the key from another XP SP3 machine and rebooted. When running either Add Remove Pro or the windows capability I received "Setup.exe has encountered a problem and needs to close. We are sorry for the inconvenience.”...........!!!
I am working on it but any ideas?