Io error when changing hard drive to external hard drive

My computer recently crashed but I was able to save my WD Protege WD400 hard drive. The hard drive has been put into a NX2 Nexxtech external box with a usb cable but the new computer will not open it. Clicking on the drive in my computer gets me the following error: request could not be performed because of a i/o device error. How do I open this drive without erasing everything on it? I am totally confused since I was told accessing this drive would not be a problem – just plug it in! Please help.

Make sure the HD’s jumper is set properly. Read Nexxtech’s manual.

Also, make sure you’ve attached the external power supply.