The biggest challenge you will face is going to be getting the PCI slots to the outside as well as the ports on the mobo. As for miniITX boards being at newegg, I haven't found any there. They might have some FlexATX boards that MIGHT fit... You'll need to change out the optical drive on the xbox for one that will work with a pc though. Oh, and any 3.5" drive WILL fit in the xbox case. I know because I replaced the 8GB drive that came in the xbox with a 160GB drive I had hanging around.