You have the master set as CS, which is cable select. This works just fine in a single drive PC. But, unless the ribbon cable that is used actually has that functionality, adding another drive won't necessarily work. You can tell by looking at the ribbon cable. If there a few wires that have been swapped just before the last connector then it is a CS cable. So, if the cable is CS, then set the TiVo drive to CS as well. Otherwise, you may need to set the original drive from CS to Master and the TiVo drive to slave. Then you need to format that drive for use in the PC.