WD My Book Essentials 2 TB problem

New hdd, one week old.

I have problem with file transfering. Sometimes it goes ok ( 100 MB/s transfer) from my local hdd to external hdd,

and sometimes it goes around 60 MB/s, but most of the time hdd freezes itself and I must restart my computer ( light in hdd blinks while transfer is active, but at some moment it begins to constantly light and thats the moment when transfer stops )

I bought 3.0 USB PCI-E card and I put it in PCI-E orange slot, cuz my PCI-E x1 slot is occupied with TV card.

I was told that this will work, and it works. I think that problem is in external hdd.




I am running HD Sentinel test almost 12 hours and its not finished yet. Sholud I continue or what ?
There are bad sectors ond hdd , and I google it how to fix them,

but I dont know should I repair bad sectors
or return hdd to the store since I have guarantee.

Any ideas ? 

Most applications that test the drive also repair the bad sectors

some times the bad sectors are too many and in that case is recommended to replace the drive