1) Root Explorer is a paid app, thus you can not post a link to it. Please refer to the rules and guidelines involving Warez.
There are free apps that can do the same thing, such as ES File Explorer.
2) Not all devices have their boot animations in /system/media. Some are in /system/customize/resource or /data/local and maybe a couple other variations. And many Samsung devices that do not have custom roms installed can't use bootanimation.zips because they have a special format called qmg and have a slightly different set up.