Awk, Perl, Ruby are probably better than sed, as could some VBScript programming (hint: open the file as a stream, and replace LF with CRLF, or whatever...). sed has some limitations on line lengths...
Me? I would have used awk (or, more specifically, gawk). In the Textutils section on the gnuwin32 website you can d/l its verson of Less for win32, as well as gawk.
Kernighan, I think, keeps the 'original' awk on his site (he's the 'K' of awk).