I have two Series 2 TiVo units, a 40-hour 540040 and an 80-hour 540080. Both are working fine. I would like to upgrade the 40-hour unit to the 160 GB drive ($119). That upgrade sounds easy enough. Can I then add the old 40-hour hard drive to the 80-hour TiVo? From what I've read, the power supply in the 80-hour unit can handle the extra drive without the PowerTrip device, but I don't know if the old 40 GB drive would need to be reformatted in some way before it would be recognized by the 80-hour unit. I'm not familiar with Linux, so the easiest solution would be the best solution for me. Thanks.