well, you can get the external enclosure electronics and hook the stuff up that way, like hdd/cdrom drive, but idk how well the cdrom drive would work. The only thing is, the rpi is designed to run from an SD card, not external harddrive, and you probably noticed by now that it wont run the normal pc software, so you cant just swap it in. If you made a custom mount bracket for the rpi, you could do it, then attach a usb hub and attach the external enclosure electronics to it, it might work that way, but like I said, it only boots from the SD card.
Ive seen a few distro setups booting from a small SD card, which tells it to boot the files off of a thumb drive, so maybe you can do that with external hdd stuff.
All in all, I think you'd spend more money on the various parts to do that than it would cost to just buy a new motherboard.
If it isnt smoking and blown into pieces, it's not pushed far enough yet.