Hello!
I have tested my external hard disk (wd with usb 3.0) with several programs.
It is damaged (only software not hardware)
1)Smart tests and "HDD regenerator" reports a huge number of bad sectors.
2)But I have also used "hdat2" from hiren CD.
I made several full test "check-correct-check" and "read-correct-read".
I always have 0 warning sectors and 0 damaged sectors.
How is it possible? Who should I trust?
(I think that every tool uses different criteria during the scans.
I am SURE that my hdd is damaged, because it's too slow, but I think it can be completely repaired if a reliable tool as "hdat2" says that is good :) ) Was this information helpful? | 
I'd like to know if you can post the screen shots of the test results?
May I know the manufacturer name, because most of the brands have their own utilities to test the drives and you can trust them.
When you use USB3, you must connect the drive to USB3 port on your computer to get the right transfer speed. If you will connect the to USB 2, the speed will be according to USB2.
I will suggest you to test the transfer speed by connecting the drive to another PC.
Sometimes the cable can be the reason of slow speed, try to connect using another USB cable.
Hope it helps.