My Thinkpad T40 started making a vibrating noise when the fan turns. It is heavier than could be created by the little plastic fan itself. The noise is cyclical, but slower than I presume the turning of the fan. Which piece is creating that vibrating noise? I cannot think of anything mobile in there but the fan. However, I do not know much about electronics.
I would be grateful for any useful advice.
More aboutthinkpad noise
The fan bearing may be going.
Get it attended to because when the fan starts making that kind of noise it isn't going round as fast as it should and overheating may follow.