There are several reasons for hard drive LED (HD LED) blinking or CPU fan getting louder when you are not doing anything on your computer.
Antivirus program, malware activity and other process running in the background of your system are main reasons.
To find out the exact reason, here is a handy utility for Windows called ‘What’s my computer doing’. This program lets you identify the exact reason of your hard-disk LED blinking or the CPU fan getting louder when your system is idle.
This program provides enough information about the process and links to Kaspersky lab and Virustotal to verify authenticity of the running process.
What’s my computer doing can be useful to find out and remove unwanted software or process running in the background of your system. Download What’s my computer doing