Most (if not all) new drives now have heat probes on them. Programs like Motherboard Monitor 5 can report these temps. For me my two 120GB Maxtors run at around 30-35C for the master and 15-20 for the slave. The difference of course is from the fact that the master is in use more often (as my slave is mostly just for storing files). Also my master is above my slave so the slaves heat rises and warms it up a bit too. Of course I got those drive bay fan things blowing on both of them (and adding to the number of fans in this case too 🙂).