Use the vi editor as follows :-
type
vi (filename) return
shift colon return
set number return
put in first line number to delete , last line number to delete space d
(e.g. 1000,200 d )
shift colon
wq (when you are happy you have deleted the correct lines)
if not happy use q! to disregard the changes.
NOTE copy the file somewhere before you do this just in case you screw up !!