Cannot run Write Hard Disk Benchmark
As the writing (like the reading) is done at various positions on the disk (some random) it is not possible to fully guarantee the integrity of the data on the disk.
In order to prevent possible corruption of data on the disk by write testing it, the disk must unpartioned, i.e. no partitions whatsoever.
Run "Computer Management" (right-click "My Computer", choose "Manage"), then select "Disk Management" under "Storage" on the left. Right-click the partitons on the disk you want to test and choose "Delete Volume".