Thanks to IRiver's Firmware Upgrade feature, it wouldn't be hard at all to put a bootloader in the player's firmware. From there it would be simply booting an OS off of the 20 or 40 GB HDD. Something similar is being developed for the H100 series, among other DAPs (
www.rockbox.org) But I'm curious as to how much of a challenge it would be to adapt Linux to the H300 hardware, rather than designing a firmware from scratch as Rockbox is doing.