If he puts it into a pc, the lack of explorer shouldn't matter, the disk will be loaded as the d:\ drive or whatever, and he can use the explorer from the working hard drive. It should then be a simple matter - as long as he sets his hard drive jumpers to make it a slave drive. That way, the working hd will be master and will boot. He may even be able to make repairs to the broken installation from the working one.
Although, he is using Windows ME. Personally, once I'd gotten the important files off I'd install XP or something better. I used to run it once and I had so many problems I hated even using it.