My lenovo Z580 lags so much ,it takes about 5 minutes for system to get started and for all the apps to work ,what should I do???It runs on a 4th gen intel core i5 processor 4gigs of ram , a nvidia gt630 m 1gb gpu, everything I do after it gets started is alright whether I play games or surf in net but it just taking a lot of time to get started,its ram usage is 50% and cpu is 7% what should I do to improve its performance pls help?