How can I eliminate the apparent Excel 2000 conflict stemming from the Excel
2003 security update recently uploaded to my computer?

I can no longer open files with Excel 2000. I have a 60-day trial version
of Office 2003 that came with my computer, but I have never used this trial
version. I always use Office 2000.

I'm running Windows XP, Media Center Edition, Version 2002, SP3.

When I try to open .xls files (which used to launch Excel 2000), Windows
Installer tries to find Excel 2003. I don't want to use Office 2003; I want
to continue using Office 2000. (Note: This situation also seems to be
happening with my Word files now, i.e., Windows Installer looks for Word 2003
when I try to open .doc files.)

I restored my computer to a date prior to the security update a few times,
but the update apparently continues to upload automatically. Constantly
resetting my computer seems like a poor solution anyway.

Thanks
KC