I have a 120gb seagate + the origional 80 gb WD in one of my R10 tivos. works great. you need to make sure that you are using a newer IDE cable. when I first put mine back together I was using an older cable and the drives did not spin up. also make sure that your first drive has the jumper set to master, and the seccond drive is set as slave. I believe the original drive comes from the factory set on cable select