The file system for the DVD drive is UDF, and even if the HDD was formatted as such the HDD is not the DVD drive, so there would need to be some FPGA witchcraft done there. Possible? Yes. But practical? Not one bit, and considering it can take an SATA drive when using an IDE to SATA adapter and the LBA48 thing was cracked years ago, there really isn't a practical point in needing 2 HDDs.