Vostro 1000 & overheating

I have 2 Dell note PC, Vostro 1000. one is at my home and another is at our office.
They works as Linux server.

About 1 year ago, Vostro at our office overheated and shutdown.
In that case, I called Dell service and he fixed it. He said the reason is dust.

Today, I encountered again. Vostro at my home overhead.
I thought I should disassemble Vostro ...? I don't want to waste holiday to do such thing ...
Fortunately, I have an "Air Duster". I tried to use it.

before:

% cat /proc/acpi/thermal_zone/THRM/temperature 
temperature: 73 C

After:

% cat /proc/acpi/thermal_zone/THRM/temperature 
temperature: 54 C

Cool!

Air Duster++
http://www.amazon.co.jp//dp/B0019SZZVQ/

But, I used its air to outlet of the fan. I can see some dust in air, though a lot of dust went to the inner of notebook?

...