Here's an uneloquent kixtart solution, removes all occurences of $string into a tempfile, meant to be renamed to original when done. Messy business...

break on

$filename = "test.txt"
$tempfile = "%temp%\test.tmp"

$string = ";Activate"

if exist($tempfile)
 del "$tempfile"
endif

if open(1,$filename) = 0
 if open(2,$tempfile,5) = 0
  $line = readline(1)
  while @error = 0
   if instr($line,$string)
    $pos = instr($line,$string)
    $newline = substr($line,1,$pos)
    $line = $newline + substr($line,$pos+len($string)+1)
   endif
   $rc = writeline(2,$line+@CRLF)
   $line = readline(1)
  loop
  $rc = close(2)
 endif
 $rc = close(1)
endif

; rename tempfile to filename here

exit 1


-Shawn