I have an external hard drive that is connected to my computer (Windows 7 Ultimate 64 bit) via a USB port. BitLocker has been activated on the hard drive to protect the data. Yesterday I started downloading a huge data from the internet but now it failed to complete because of CRC error. I tried to repair it with chkdsk f:/r where f is the drive letter of that hard drive. There are many messages reporting "unreadable" as follows: What caused Cyclic Redundancy Check error on my BitLocker-enabled external hard drive and how to fix it?