I have successfully booted via grub from the Hard drive. That is, I was able to download the iso, but could not use a DVD drive. This is a useful way for someone to use rr4 with out a DVD drive.
1/ I mounted the iso via -o loop
2/ copied everything to a HD partition
3/ edited the Grub menu.lst to include an RR4 option
4/ rebooted and rr4 is running beautifully
I have used knoppix, kanotix, slax, goblinx, puppy but this is the first Gentoo.