Laptop problem

[wnf15]

My sister has a Acer Aspire 5920G Laptop (http://www.popvoucher.co.uk/cheap-acer-aspire-5920g-laptop_lid-cmoqmmqp.html), she says it cuts out frequently (the fan turns off and the screen goes black). I've never had this when I've used it although I have noticed the fan is noisy and the laptop gets very hot, it feels very warm on the keyboard. I've had a look at the fan and there doesn't seem to be much fluff so I'm thinking it's the fan and I'm tempted to replace it.
My only concern is that it if the systemboard controls the fan it might actually be the system board that's faulty. Just after a second opinion really, anyone have any suggestions?
Cheers

[RecT]

I must confess to never hearing one of those overheating. Usually its the old Pentium 4s that had heating problems - but I would imagine that the cause will be the same.

As the computer gets older the heatsinks get clogged with dust and other cr*p. Take a few cotton buds to them and the fan will have to do less work to keep the laptop cool.