Hello everyone, i have got an issue with my sony vaio vpceh28fg which is almost 6 years old now. Somedays my laptop boots normally but feels very laggy in performance and other days it shows black screen at initial boot up with message- operating system not found, press alt+ctrl+del, upon pressing these keys again and trying for 4attempts the laptop finally boots but is very laggy. The other issue is that there is a sound like constant clicking heard from the laptop. I visited a local repairing center and they said it was just some dust in the fan and they cleared it, after which the sound has disappeared but the os not found message still pops up. I suspected there to be a harddisk error so i tried this hd tune pro software which showed nearly 5% damaged blocks. So what is the best option for me to do now? Please guys help me at this issue.