The IMG format might load with Paint Shop Pro 9 - which I think can be downloaded for free. It has a lot of historic formats that it supports, so it's a good package to have installed regardless.
The .SPR format, well it might be a derivative of IMG, like an IMG file laid out in a specific way, raw IMG data - or it could be a specific format just for the game.
EDIT: Looking into it more, it appears that the SPR format is some header info, sprite image count, size etc, and compressed image data after that. It's probably not the sort of thing you can rip from... Sorry to say but I don't think you'll get far with the SPR format - you'd probably save time in the long run by screen grabbing, or even making new visuals for yourself, based on the original. Even if you can only manage some boxes, you could always pass it onto an artist later.
It can be tricky to even identify files like that. Often, people will just rip the graphics from screenshots the slow way, because there's no easy file support.
I miss the old days, when you could just reset your computer and use a program to pick through the memory - I nabbed so many cool sprites this way. It's one of those cases where progress is making your job more difficult.
I am the one who knocks...