I recently installed Norton Security 2015 OEM 90 days trial and I saw the performance feature. I clicked on optimize disk and it was finished quickly. Only C drive was optimized others didn't need as it said. Later my PC start hang and I manual restart the PC (I was using windows 10 x64) but window startup screen was just rolling up and it didn't open. I thought it must be a virus problem so I decided to format my PC. I boot form DVD and setup was taking too long to load and finally I tried to format C drive but it failed and again I reboot and didn't saw any partition. I took my PC to a technician and he said your hard disk is damaged you need to change it. I asked for data recovery but he said it is not possible in my area. You must have understand how I felt all my videos, photos and datas were gone.... They installed Windows 10 64 bit on new hard disk and I again decided to install same Norton security OEM 90 days free trial after 7 days. I didn't use disk optimization feature and I felt my hard disk is safe but what I later found is Optimize Disk feature runs in the background when the computer is idle. Firstly my PC start hang and I doubted that it is the same problem. I restart my PC and later went to the Settings and disabled disk optimization from Task Scheduling option.
Now everything is OK but Symantec need to think about this bug that caused me a heavy loss.