When talking about drives, there is a difference in a 'bare' drive and an 'oem' drive. A bare drive is what you would buy from Newegg, MWave, local mom&pop shop, etc., and IBM warranties them all for 3 years. An 'oem' drive is one that was shipped inside a Dell, Gateway, HP, etc., machine. Those drives were sold to those manufacturers at a lower cost with the agreement that they would handle all warranty claims. (usually the same as the PC warranty)
Unless that was a drive that you removed from a Dell/Gateway/whatever, it should be covered.