Need help from a computer whiz please

[Freespin]

For some reason when Mum transferred photos from her camera to her computer they decided to be NEF files. She was unable to open them so emailed one to me. I am able to open it in GIMP but they only show up tiny (160 X 120) even though it says its 10.7MB. Anyone have any idea how to fix it? They are pictures of my dog from his very first agility show so i would really like them =/
Apparently they automatically delete off the camera when she puts them on the computer.

 

[MikeyTN]

When you first transfer it should of give you an option for what type of files you want to save them as.
so right now you can visit this site to download DNG converter so you can convert from NEF to DNG. Camera raw, DNG | Adobe Photoshop CC

 

[WannaBeAParrot]

Also, there should be a setting to stop the photos from automatically deleting from the camera if you prefer to first check the download on the computer first.

 

[MonicaMc]

I wonder if it would be possible to transfer the pictures back onto the camera, then remove them again in another format?