"The drive ""interface"" or drive controller supports 3.0Gbps, but the drive itself does not have that kind of speed. The drive you have is a ""green"" oriented drive with a slower 5400rpm spindle speed and focuses on low power requirements (hence, the ""green"" label).
The 3.0Gbps rating is the SATA 3.0Gbps controllers potential throughput. The hard drive is connected to that controller, but that drive is not capable of those speeds.
30-40 transfer speeds actualy sound like a normal average transfer speed to me for that type of hard drive. You could make sure your operating system is very clean and running the latest motherboard/hd controller drivers to possibly speed things up a little. The most noticeable difference however would be seen if you upgraded to a better performing hard drive. One with at least a 7200rpm+ rotation and performance intentions. And if you got the $$$, SSD drives would bring you even more speed."
"One possibility for a slow disk is when Windows downgrades your device DMA mode when CRC error occurs along the interface. See this article: The stuttering DVD drive or the lame hard disk. If that's the case, you should check the hard disk for bad sectors.
Another possibility is if in the Properties of the drive, Hardware Tab and again Properties of the hard disk, ""Enable write caching"" and ""Enable advanced performance"" should be checked."
