text: up to how many days will a hard disk last if it is turned on 24/7? i was planning to host my own web server on my computer. but then i had this incident where i was downloading  from the torrent network. and i turned my pc on for 4 days straight i think.... and then on the last day, it was at 90% of the whole downloading process when suddenly my computer hanged. when i restarted my pc... i cannot boot anymore. so i reformatted it and then it started out cleanly. but then... all of what i have downloaded(8.57gb!!!) was erased!!!! so, i was traughmatized of that incident so i asked this question. now back to the question, up to how many days can the hard disk be turned on before shutting it off to make it rest? how long is a piece of string?  a hard drive can function indefinitely sans manufacturing defects or extreme heat.  i have 2 primary hard drives and 2 external drives running on my machine 24/7, only rebooting when a necessary update is required and things are fine.  a hard drive is the only mechanical part of a computer and as such will at some point fail.  but when that is can not be predicted.  i would say 90% of the time it would work faultlessly until you are ready to change your machine