Hi, I'm a total pc noob so please bear with me.
I've noticed the past few days that my 2 yr pc makes a slight buzzing/whirring sound when on but remains when I turn it off. The noise only goes away when I switch off at the mains and starts back up again once I flick the switch back on. I'm quite wary of opening the pc case up as I have no idea what I'm looking at but any pointers will be most appreciated. Also any cleaning tips would be appreciated as I'm sure the fact despite not living in a hovel there will be a bit o'dust when I open it up.
Thank you.

I've noticed the past few days that my 2 yr pc makes a slight buzzing/whirring sound when on but remains when I turn it off. The noise only goes away when I switch off at the mains and starts back up again once I flick the switch back on. I'm quite wary of opening the pc case up as I have no idea what I'm looking at but any pointers will be most appreciated. Also any cleaning tips would be appreciated as I'm sure the fact despite not living in a hovel there will be a bit o'dust when I open it up.
Thank you.