CRC is a checksum. Having an error in one means the sector has some bits out of order, corrupt or missing. File reading programs may not take the chance the data is good and just report the error. If you can tell the program to ignore the CRC and open the file anyway, 9 times out of 10 you’ll have a minor error in the data. The tenth time the error will be in the housekeeping data, and the file will not reconstruct, or you’ll get a whole sector of garbage. If you have a hard disk sector reading program, you may be able to work around a CRC error, but it’s time consuming and requires detailed information about how your hard drive is formatted at the hardware level.