Can i use VirtualDub to create black boarders

Hi, i have an avi video file that has subtitles in the black boarder at the bottom, can i use VirtualDub to over-lay a new black boarder to cover them up.

And is there a program that can do the same but with mkv video files, please excuse my terminology as i'm sure there not called black boarders, thanks.

 

See if this applies.

http://forum.digital-digest.com/archive/index.php/t-39726.html

 

Thank you once again attar, i should have searched the afterdawn help guides but needed a quick fix as i'm off line soon for some time. thanks for your help.