I've noticed a lot of people reporting various problems with this product on the internet and, from what I can tell, most of the time it's because of incorrect application or installation on the part of the user. I've installed this product on 6 different motherboards with 4 different types of SATA hard drives and have had no difficulties with any of them.
First, this device is meant to allow someone to connect 1 or 2 SATA drives to a dual IDE port on the motherboard. Not the reverse.
Second, if you are installing only 1 SATA drive, it must be connected to the first SATA connector, (the one on the opposite side of the board from the SP4 power connector). If you're installing 2 SATA drives, then this port is the Master and the SATA port in the middle is the Slave.
Third, this unit requires its own power. The LP4 to SP4 power adapter supplied with the unit must be plugged into the SP4 power connection on the unit and an available LP4 power connection from the power supply. This connector isn't meant to power the SATA drives. They must have their own power connection from the power supply.
Fourth, if you happen to have one of the older units, the jumper on it was never implemented (per StarTech). It does nothing. The newer units don't even have the jumper pins mounted on the unit.
Lastly, some older motherboards require the SATA hard drive be limited to 1.5 Gb/s speed in order to "sense" the drive depending on the model of the drive. This can be done with a jumper setting that can be looked up on the manufacturer's website of whatever model SATA drive is being used.
Hopefully this will help some people out with problems they're having with this product.