An other and easy solution is to use the Begin/End Select feature !

• 1 Left click at the very beginning of the first line 0000 90 9F 33 .. .. .., to move the caret to this location

• 2 Select the option Edit > Begin/End Select

• 3 Use the Ctrl + End shortcut to get the very end of your hexadecimal dump text

• 4 Press and hold down the ALT key and left click after the 16th hexadecimal byte of the last line

• 5 Select, again, the option Edit > Begin/End Select

=> After a while, needed to process 400,000 lines about, as you said, you should notice this big rectangular selection !

• 6 Simply, press the Delete key

Voila :-))

Best Regards,

guy038

P.S. :

If you forget to hold down the ALT key, at step 4 of the method above, you, obviously, get a normal selection of all your text !

even in this case it would be easy to do it.

Click on the starting point
scroll down to the end
press and hold SHIFT+ALT and click with the mouse to the end point.

Note, I don’t want you to refuse using regexes,
just want to make sure that some actions can be done with using it,
especially when it comes to rectangular selections, easily.

From your picture, I suppose that the following regex S/R should work !

SEARCH (?-s)^.{56}

REPLACE Leave EMPTY

Notes :

• First the in-line modifier (?-s) means that the regex dot char ( . ) matches a single standard character only and not the line-breaks \r and/or \n

• Then, from beginning of line ( ^ ), it matches the first 56 characters of any line… and deletes them, as the replacement zone is EMPTY

Best Regards,

guy038