Decided to clean one of them up tonight, it has 10MB of RAM and a 250MB HDD. It is actually a Performa 250, and was used at a school.

It would load to a Happy Mac, then ask for a disk. I dug out the Apple CD300 I just got, and was able to load 7.6 from CD, which I then installed onto the HDD which was recognised. All the original files are still on it, so there must have been some sort of issue with the System files being corrupted. Works great, just like the one I used to use when I was 10.