A “Bad Sector” is a term for a broken piece of Hard Disk Drive (HDD)–a very small piece. There are millions of sectors on a hard drive. EG, standard sector size is 512 bytes (aka 512B). Consider a typical disk (in 2015) of 1TB in size, or 1,000,000,000,000 bytes (1 trillion bytes). Doing some math: there are 2 million sectors on a 1TB hard drive.
That means everything you store on there is broken up into pieces of 512. Have a 100MB video file? It is stored as 2000 pieces of 512B each.
Fortunately, when sectors go bad, two mechanisms exist to help you.
- The hard disk drive itself detects many bad sectors and remaps them so that data is stored elsewhere, in good sectors. You may never notice these.
- Windows Operating System detects bad sectors and marks them to avoid using them in the future. Windows Vista, 7, 8 (and presumably 10 and later) detect when a “chkdsk” is necessary and prompt you to run it at next boot. If not, you can run “chkdsk” yourself.
Note: when the OS detects hard disk errors, you should IMMEDIATELY MAKE A BACKUP. DO NOT PASS GO. DO NOT COLLECT $200.
Then, get a new hard drive.
Usually things will only get worse. In the upcoming months, even days, even hours.
Why do sectors go bad?