Record sound playing on laptop or computer

Right-click Speaker icon on Windows Taskbar and select Recording devices

Click Recording tab

 Right click in empty space and select Show Disabled Devices

You will see Stereo Mix
If it's disabled then enable it : Right click Stereo Mix device - Enable

Right click Stereo Mix device and select Set as Default Device

Click OK

Now play Audio recording software and record the sound playing on the system.

Check system Up time from command prompt

Open command prompt

run this command
systeminfo | find "System Boot Time"

Check how long system has been running without restart (Up time)

Open Task Manager
Click Performance tab
Click CPU

You will see Up time