i do not know the safe EXACT temperatures of hard disks, but this is not rocket science. put your hand on top of the hard disk. if it is warm you are OK. if it is hot than it is overheating. if it is scalding hot than you have something that needs fixing right away. hard disk usually get too hot if something right above it is blocking the air to cool it off. you need to leave space for the hard disk to cool off below and above it. if nothing works, you can install a cheap hard disk cooler, these can be found on newegg.com. the speeze cooler and the vantec one are the best, they screw to the bottom of the hard disk