> Find . -name "*.htm" -exec 'sed s/old/new/' > '{}'.new


the above command is probably a sytnax error, due to unterminated
-exec (add \; at the end to fix this), that apart that command should
look for a command 'sed s/old/new/' (note: it should NOT invoke sed
command with s/old/new/ argument).


find . -name "*.htm" -exec echo '{}.new' \;

should do what you want.



-- 
almir