I have purchased external hard disk from amazon.
It has good speed and compatible with win 7, 8, and 8.1.Segate is provide three year wrranty on hard disk. I have created an account on segate official website and entered my details of external hard drive and using it. The product quality and performance is better. It has speed upto 35 Mbps on my system which has win 7 opearating system. Those want secure storage for them product is excellent.