Why Is There An Occasional Disk Read Error At Windows Startup

I unplugged the SATA cable and power cable of my hard drive (Western Digital WD2500AAJS) and re-plugged and it started. I started my PC the same way today. This happened 2 times last week and every time I had to do the same to start my PC.

Kindly tell me what is the problem and what to do? Should I change my hard drive? I already made a back-up of my data.