HP Laptop motherboard problem- Veeeery slooooooooow

Hello All:

My HP NX7400 laptop started running extremely slow.

I tried to run two different OS's that boot and run from a CD and the performance was still very poor so I have excluded any Hard Disk or the installed Operating system problems.

I took the computer to a local dealer who said that it is a motherboard problem and I need to replace it. He quoted a large amount of $$, definitely not worth spending. He said that the problem occured because the computer fan was full of dust, that prevented good airflow, resulting in the overheating of the motherboard.

I have 15 yrs of exprerience and I have never seen a motherboard problem (desktop or laptop) that simply slows the computer down, NO freezes, NO reboots, NO blue screens, NO black screens.

Does anyone have an idea ? I thought that with some help, this may be the best opportunity I have to try and fix a motherboard, since the computer is otherwise working fine.

Many thanks !
Andreas