Cyclic redundancy check error code 0x80070017

Every time i try to back up my files to the hard drive i get the above error code showing up on data(d) and it keeps saying last back up failed. I have done a disk check and it came up with number of root causes 1. Whatever that means cause i am a 60 year old layman at this computer game. I have defraged my discs as well, but i still keep getting the same response.
So if somebody could help me with this problem in a non tech language that i can understand, it would be very much appreciated.