Installed Office 2000 SP3 and "redline" fix, then tried to install Ken Slovak's ADDOPT. Part way thru installation I get a "1391 error, Windows Installer service cannot update the system file C: WINNTSystem32comcat.dll because the file is protected by Windows. Checked file properties and it is not "read only". Downloaded and installed latest Windows Installer; no help. Any suggestions? Thanks a lot. Karl