Rom file size related

What is the program that shrinks the size of roms or deletes the empty space?

If you wanna save space on your comp, just compress it in .rar or zip.

I read somewhere that there is a certain amount of hard drive space in the roms that can be shaved off. I just want to do it to fit more roms on my game cart.

You want a rom trimmer. Google NDSTokyoTrim.

You can use this NDS Tokyo Trim to trim the garbage data off of the NDS/GBA roms. - http://eden.fm/ndstoykotrim/

Thank you for the info, it is appreciated.