As a general rule for SATA drives, do NOT change anything on the jumper block. The one item some people need is that mentioned by noidea_77 - forcing the HDD to slow down to the slowest SATA data transfer speed, but these days it is RARE that anyone needs this. On the other hand, placing a jumper in the wrong place can make your HDD appear to have failed completely (it has not, but it behaves that way), so don't change UNLESS you know what you are doing and why.