I looked before I lept and need help

[fragtagger]

Hi There,
I have an Iriver h10 20 gig. I've been using rockbox on it fine for several months.
I had put 5 gigs of audio dramas on it for my son.

But it always bothered me because for some reason, when rockbox was installed months ago it did not have access to all the data room on the hard drive. For some reason, about 14 gigs was still my old music that was installed via the old software.

I wanted to get rid of that music, and just have the data room for my son.
So I finally sat down to do that today. I figured I'd just reformat the hard drive and reinstall Rockbox.
So, using disc utility on my mac, I mounted the H10, and reformatted the whole darn thing with fat 32.
I begin the rockbox reinstall starting from scratch, and get the error:
"copying modified firmware file failed" during installation of the bootloader.

I suspect that I need to have something already on the iriver hard drive? I'm a little worried because I do not own a PC, only macs, and don't know how to get any of the original iriver software on it.
Any thoughts?
Thanks