What do you mean rename it to its original name? and mostly included inside, in the file: namecheck
>_>
Example:
You download M16 from the archive.
You have to rename the zip file to Weapon_M16 to make it work.
/Example
Most of the times, a namecheck textfile is inside a add-on zip file, that checks the name of the file.
If the file hasn't got the same name as the one written in the namecheck file, it get's disabled.
Easypeasy.
EDIT: The sandwich would be Item_Sandwich if i am right.