I was called Apple and asked some questions about replace the different brand of hard drive, even more space or more speed. They told me that wouldn't void the warranty if you installed new HDD so properly, even not make any damage by HDD replacement, if so then would void your warranty. If you installed it so properly and haven't any problem that related to HDD then you are still under warranty, same goes applies to Apple Care. If Apple Care was voided after they found any damage from HDD replacement then you are still under phone call support, it would cost you for repair the parts if warranty was voided or expired. Is it safe to put WD 320GB HDD in MacBook Pro? I did bought WD 250GB HDD and installed it then found the failure from SMART then replaced back to stock HDD. Does WD 320GB HDD is much improve over WD 250GB HDD?