Only the dimensions, electricity supply and interface (plug and instruction set like ATA or SCSI) of a hard disk are standardised. The rest is to the manufacturer leave. Another model is simply another computer (see the first question). Also within a model there are often constructive differences.
Solutions to hardware problems are very strong related to the specific model. One should be very careful while taking advice from forums or from experts who are not interested in the model of the hard disk.