Originally Posted by Hlingler
What do you mean: "load completely into RAM" ?
A live CD/DVD OS IS running completely in RAM (except for SWAP, if any Linux SWAP partition is available on HDD).
If you have a LiveCD and have sufficient amount of ram you could run from ram and eject the LiveCD to free up the cd/dvd drive.
EDIT: I dug out an miniDVD-RW that had "Fedora-6-Zod-LiveCD-1" still on it and at the boot menu you could choose to "install to ram" and eject the cd.
During boot up on the kernel line was "livecd livecd_ram" took a few minutes to load to ram though.