Installing Upgrade from Office 2000 to Office 2003 Professional

[FraserH]

When I run setup I get the following message from Windows Installer:
"This patch package could not be opened. Verify that the patch package
exists and that you can access it, or contact the application vendor to
verify that this is a valid Windows Installer patch package."
I had no problems with is the first time. The problems began after
installing Office 2003 Service Pack 2. Eventually, I uninstalled Office 2003.
After re-installing Office 2000, I get the message above.
Fraser