I have an iMac (Rev. A) with 128MB RAM and Maxtor 40 GB HD. I just installed OS 9.1 and when I first installed it I put it on a 4 GB partition just to try it out and make sure it worked. As you know you can have up to an 8 GB startup drive on a Rev. A. But when I transferred all files over to my 8 GB partition my iMac refused to start. So booted off the OS 9.1 disk and updated the hard disk drives and ran a Disk First Aid and restarted, still no luck, so I transferred it all back to my 4 GB partition and all of the sudden it starts up.... Looks like Apple doesn’t like us Rev. A iMac users!!