If you have had the drive for 18 months, it is very likely out of guarantee/warranty.
If the fault is only occasional, then it might not be the drive at fault.
Spuds is quite right about Amazon being first class at resolving returns issues - I once returned a set of Logitech 5.1 speakers after 18 months (two year warranty) and within a few days I had a full refund, plus the cost of returning the speakers by ParcelForce.
"If an item is found to be defective after the 30-day time frame, we do suggest contacting the manufacturer to try and resolve the issue, as they are in a better position to provide additional support services for their specific products. We recommend consulting the manual that came with the package for warranty and service information."