This laptop is ten years old now, so there can't be too many about, but if you do have one, here's how to clean it.
Not by taking out every screw on the bottom of the laptop, which is what I tried. Just take out the two screws in the back behind the multimedia keys panel and gently pop it out, then the keyboard will lift up to reveal the fan.
Or I should say fans, because there are actually two. There's one conventional fan which blows air through a grill connected to the heat sink, and another small circular propeller-type fan in the back on the right whose purpose was not clear to me.
The heat sink grill was not especially dirty considering it hadn't been cleaned in ten years, but enough to restrict air flow.
It's surprising considering the fact that laptop fans need regular cleaning how difficult they can be to access, especially when you don't know what you're doing.
With a nice clean fan, the laptop runs Debian Linux just fine, even if it is ten years old. Dig out that old laptop, clean it up and give Linux a spin!