External HDD not recognize my laptop & cann't initialize it from Device manegment

I've a External HDD( Western Digital company-500GB) which was working properly last night but today it's not working. when I connect the EXt. HDD to my laptop usb port then it's got power but not shows in my computer.
when I go to device management it shows a window (you need to initialize before logical disk management can access it.) but when I go to initialize the HDD then show it "the media write protected". I cann't initialize the HDD and cann't access the HDD.

Someone help me to recover my old DATA from this Ext. HDD.

Thanks for advance.
Hello Rajib Sarker,
The first important thing to note here is that if you initialize your HDD you will lose all the information that was stored on it. Sometimes portable external HDDs can behave like that if they are not getting enough power. It would be a good idea to try and connect your HDD using a different USB cable, preferably a short one. Another thing you can try is connecting your HDD to different USB ports and to a different computer. You can also run WD DLG diagnostics tool to test the HDD http://products.wdc.com/support/kb.ashx?id=GTBpZQ .
Hope that helps.
Thanks Techpumpkin_WD for your response.
1. I already used another USB port & Cable but not solve.
2. As per your reply I try to diagnostics HDD by using WD DLG but not solve. when I check it by EXTEND TEST then it shows " To many bad sector" and fail to test. But QUICK TEST result is PASS.

At lest please help me to recover my old data from this HDD.