i think i know what you're talking about... if it's something like a "windows file protection" error, then try this:
goto "Start"
then "Run"
in the "Run" box, type "msconfig"
click "OK"
on the "General" tab, select "Selective Startup"
clear all the checkboxes
click on the "Services" tab
select "Windows Installer"
click "OK"
restart your computer
try reinstalling office now...
hope this helps. good luck.