text: There are reasons, and mainly they have to do with power supply kicking off, pulling a lot of current and then your hard drive spin up. They are using air as bearings for the drive, so they float when running but when off sit metal on metal. \n\nIt is like starting a car, a lot of things are happening and typically that is when a car fails. \n\nAlso, if you mean just rebooting all the time, that is because windows creates virtual memory allocations of your hard drive for swap memory. These tend to get fragmented and take up a lot of memory if you just power off without shutting down. If you have done a lot of these, just fragment your hard drive and that will clean up the fragmentation, just not the files themselves.