The good news is that it can be fixed by yourself, typically in under 5 minutes. No incorrectly diagnosed (and very expensive) motherboard upgrades are needed. All you need is a screwdriver and a vacuum cleaner. You might even get away without the vacuum cleaner :-)

Much like vacuum cleaners a laptop switches itself off if it gets too hot. This is to protect the valuable brain of the computer, its main processor or CPU, as well as our precious legs. Also similar to other things that overheat, the problem is often caused by excessive fluff build up in an important area.

On a laptop this crucial area is the fan that sucks air across the CPU to keep it cool. This point is important to absorb... inside a computer a fan is used to suck air across the CPU (which heats up).

After about a year or two of use, many laptops build up layers of fluff in the fan area that are thick enough to stop the flow of air. This means the CPU is not being cooled properly, it overheats, and the safety mechanism kicks in and shuts the computer down. You experience it as a reboot. (Geeky fact:- There is a mini temperature sensor built onto the main chip itself that constantly monitors its temperature)

To be absolutely sure you have the problem I describe, ask yourself this question... After your computer has switched itself off for the first time in a day, and is switched back on again, does it switch itself off more quickly the second time?

If you leave the laptop to cool down, can you run it much longer before it switches off?

If the answers to these questions are yes, you absolutely positively have an overheating laptop causing your reboot problem... don't let anyone else tell you differently.

As an overview, what we are going to do is find the place where the fluff is building up inside the computer and remove it. This should fix the computer instantly with no further action required. Hooray!

Turn your laptop over and look at its base. Somewhere there will be a panel that you can remove with a few screws, that gives you access to the main processor and fan. Most likely there will be several panels you can remove with a few screws - but don't worry - I'll help you find the right one.

Incidentally, not every laptop allows access to its main processor and fan (Apple laptops typically don't). Some use other mechanisms besides screws e.g. catches, latches etc.

Before you start removing screws randomly, and any descriptive icons which are present are undecipherable, there is something you can do to zero in on the right panel.

Turn on your computer, wait for the fan to come on, and work out where the hot air is blowing out. Normally the panel you seek is close to this. If you can't hear a fan, you may have a broken fan - this would also cause the same over-heating problem described, but is naturally much trickier to fix. If the fan is simply stuck, eg with fluff, the instructions below will help.

I'll now show you how the panel and fan looks on an Acer laptop (an Aspire 3003LM ZL5 to be precise) and this will show you what to look for on your own machine.

On our Acer laptop, the panel we're interested in is at the top left of the laptop when you are looking at the underside (labels reading correct-way-up). I found it by feeling around for the scalding hot air coming out that corner.

3 screws hold the panel in place as shown.

With the screws removed and panel lifted off, you can see the fan which cools the CPU (via a bronze air tunnel). I've turned the machine around 180 degrees for this photo. Different laptops have different configurations, they might not have air tunnels for instance, but the basic principle of sucking or blowing air across the CPU remains. On this laptop, the fan is enclosed in its own mini-housing with 3 screws holding down the top cover. These 3 screw locations are shown.

You really don't need to worry about which bit is what however, simply look for fluff build-up around the fan and in any areas that could be 'airflow areas'. A common area for fluff build-up is the inside of the vent which takes the hot air outside. You can see this on our laptop below.

Using common-sense, prise, suck or blow away any 'fluff blankets' that are restricting the air flow. Sometimes these fluff blankets are so compacted, and come away so uniformly, that you think they are supposed to be there as some kind of... insulation - they are not!

If you use a vacuum cleaner and suitable attachment, you can have fun 'sucking on one side of the fan and making it spin round' very quickly. I actually look forward to this part of the procedure because apparently I'm an overgrown child.

With fluff removed, your fan area should now look a lot cleaner, and clearer. Blow on everything one last time to make sure...

If you've successfully and with some pride pulled away a compacted blanket of fluff, you can now feel pretty chipper, announce to family or dog 'I think I've fixed it', and carefully replace the bits and screws before turning on the computer to test it. You're done basically, come back and check out the rest of my site please another time :-)

If you've hit a roadblock... for example fluff you can't access because it is hidden behind something important looking, use your common sense and evaluate your own skills. Removing the CPU, fan or heatsink for example can be tricky and can lead to bits breaking, although these components are among the cheaper and easier things to replace. You must make the call.

If you have experiences to share, love to give, or other musings, please leave your comments below. This has been one of a growing series of Layman's Guides, written as I come across problems I need to solve. They now include...

Fixing an overheating Dell Inspiron laptop
What is RSS? And why do I care?
Converting FLV video - A Layman's Guide
A Review and Guide to CamTwist Video Software
Syncing a Blackberry Pearl with the Mac Address Book
How to get David Letterman tickets
Accessing MovieLink and CinemaNow from outside the USA
An overview of the current InternetTV landscape
Glossary of Online Video terms
A Layman's Guide to the UDRP

If you've enjoyed this post you can receive future musings, as I write them, via email. I post about once a week on average. More techy folk might prefer to subscribe to my RSS feed and I'd be delighted if you do. I'm rather more active on Twitter, have a few pictures up on Flickr, and I tend to keep track of people on LinkedIn and increasingly-less-so Facebook. My day job is running WorldTV.com - a site for doing cool things with online video.