I have a Dell Inspiron N5010 Laptop with Windows 8 Pro 64 Bit installed and earlier this happened for a moth and my HDD Failed and replaced it and again after plugging it the disk usage still goes high. I don't know what is causing this. sometimes firefox or other apps lags for just a second and then returns back. at that time the disk usage will be very high and my hard disk status is ok in Hd Tune Pro. In Windows 7 there is no problem. Only problem is with windows 8. I am afraid about it. Kindly help me.