I currently am running Win XP SP1 v.1102 and Office 2000. I just attempted to upgrade to Office XP, and while installing Office SP1, I got an error message stating "Error applying this patch to file C:\Config.msi\pt1c.tmp. It has probably already been updated by other means and can no longer be modified by this patch."
What do I do? If I cancel, the install fails, if I hit retry I get the same error....
When Office XP came out and some people got hold of a type of key that doesn't allow it to be activated (similar to an XP Corp Key) when people upgraded to OfficeXP SP1 those types of errors were common. The way to do it is to slipstream the SP into Office and install. Some notes around about how to do it. That will solve your problems.
I am pretty sure that your copy of Office XP is a "prerelease" corporate version that leaked prior to Office going RTM. This version of Office XP also gives the same error when attempting to apply SP1 or SP2 patches. You need to get the full corporate version and your problems should go away.