100% disk usage

Operating System
Windows 8.1 Pro 64-bit

CPU
Intel Core i5 2400 @ 3.10GHz 51 °C
Sandy Bridge 32nm Technology

RAM
4.00GB Single-Channel DDR3 @ 665MHz

my PC starts to hang nd in task manager is see these 100% disk usage.
how can i solve this error?
i have already disables super fetch ,prefetch

plz help