I can't imagine that OneCare had anything to do with that, but anything is possible with computers.
What I find odd is that Office 2000 reports being expired since it isn't a subscription product.
I suggest that you contact Office support - start here:
http://support.microsoft.com/ph/2484Note that Office 2000 support ends in July -
http://support.microsoft.com/gp/lifeofficeYou probably should consider getting Office 2007 Student Teacher edition - often available for around $100.
You can also pursue this with OneCare support if you believe that it was the cause:
How to reach support (FAQ) - http://social.microsoft.com/Forums/en-US/onecareinstallandactivate/thread/30400b52-7f26-4ba0-bc18-17e305329d90
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator