Dell has admitted that a 'small percentage' of its Inspiron 5100 notebooks have been experiencing overheating problems and that a fan vent has been redesigned and the Bios tweaked on later models to prevent this.

The admission came after Chris Richardson, a reader of Personal Computer World, contacted us when Dell demanded £325 to replace the motherboard on his 5100, a month after the end of his one-year warranty.

He discovered US postings complaining of a problem with the machine stemming from a dust build-up on the heat sink.

One, geocities.com, gives advice on how to deal with the problem.

Dell has agreed to replace Mr Richardson's motherboard and extend his warranty to three years as a 'gesture of goodwill'.

Dell said in a statement that the 5100 was designed to shut down if it overheated: 'However, we recommend that... customers experiencing this issue have their systems serviced under the Dell system warranty.'

The statement added: 'We would like to stress that this issue pertains to a very small percentage.'