an rma would be if you bought it from somewhere like ebuyer or dabs or aria etc--if its off ebay then its a bit different and depends how helpfull or awkward the seller is--they might replace it with no fuss or might try to say you damaged it--they might have put no returns on the listing etc
if they get awkward it can take weeks to sort it out through paypal and ebay though you will likely win anyway by saying its not as described as it was sold as new and therefore fully working--though you will get hit for the return postage make sure to send it back recorded delivery
use ebay contact the seller to see how they respond and if necessary then you can open a dispute
He has replied to an email saying "It should be fine have u made sure u formatted it to a spare data drive not a system drive? With the click sounds on drive, it didn't do that at all here before postage. hope the post didn't loosen something"
well you cant format it at all if connecting it makes your pc unbootable and the steps you tried with the cables and stuff were totally sensible ways to double check if the drive was faulty--as well as the clicking and beeping i would say its faulty
how well was it packed? and whats his feedback like?
i would insist on a refund or replacement quoting to him the steps you tried and take it from there if you have to open a dispute if you get no satisfaction then do it--ebay usually will side with the buyer in these cases as he cant prove it was fully working when he posted it--he can claim up to about £32 even if it was not sent recorded for postal damage and about £40 if it was recorded without any extra insurance