Upgrading a notebook computer can extend its lifespan, improve your end-user experience and reward you with the knowledge that sometimes you really can teach your old dog a new trick or two - though, in most cases, that's entirely up to the dog.

The article gives a very nice overview of what to do to an old laptop. I'd like to add a few remarks though:
- some laptops don't enjoy non-branded memory modules: IBM ones for example, won't appreciate RAM that has not been tested for them (avoid generic RAM with those).
- a hard disk upgrade can actually boost performance: switching a low-cache, slow-rotation hard disk for a more recent, better equipped one can yeld a tremendous boost in application loading, increase battery life and reduce noise (switching from a 512 Kb cache to 2-8 Mb has incredible effects)
- upgrading the OS is not always a good idea: for example, switching from Win98 to XP may lead to lost power management features, worse driver support and non-working hardware.
 
Personally, I did the following to an IBM Thinkpad a21m:
- increase RAM to 384 Mb
- swap 20 Gb, 2 Mb cache drive to 60Gb, 6 Mb cache drive
- install a Linux flavour with Xorg 6.9.0
 
That machine can't do a 3D interface (Mach64/Mobility M1 3D support is too puny), but it runs Google Earth, OpenOffice, plays back DivX movies, plays SuperTux, accesses all my websites (banking and video streaming ones included), does dynamic CPU frequency scaling, supports suspend to disk...
 
It's cool

Upgrading the HDD and sometimes RAM can yield large speed dividends, but I strongly disagree with the assertion that upgrading to a newer OS can improve performance. Newer OSes are always more resource-hungry than older OSes of the same category as there are newer features that consume more resources. This is true of all OSes. Windows 2000 generally runs faster and takes less memory than XP on older machines as 2000 lacks the extra fluff and GUI gaudiness that XP brought to the table. And XP runs phenomenally faster than Vista as Vista REALLY dialed up the GUI and added a whole DRM framework that always runs that also consumes RAM, HDD space, and CPU time. Newer Linux distributions generally follow the trend of requiring more resources than their predecessors, but it's not quite as bad and easier to fix than in Windows.  
 
If you have on older laptop, realize its limitations and usefulness. Don't expect an older laptop to be able to transncode a 3-hour-long DVD movie in any reasonable time period. Nor should you try to put extremely resource-hungry software on one. Older laptops are good for the kind of tasks that laptops were originally designed for: mobile word processing and office applications, e-mail, Internet access, and the like. Just don't expect them to run Oblivion at 100 fps and you'll be fine.

Not a bad article, but I agree with the other comments regarding the OS upgrades.
 
I used to own an old Compaq Presario. It ran great until one day the hard drive died. Then I began looking into upgrades - I switched the hard drive, saw that I could add more ram and could even remove the optical drive and add a DVD burner.
 
The really cool thing about the machine though was that it had a removable video memory module, letting me go for more VRAM as well. The modules were as scarce as hens teeth, but the extra video ram gave my software the boost they needed, especially because the video module itself was not upgradeable.
 
My current laptop is a different story. The video module and video ram are both soldered on the motherboard. They are not upgradeable. However, after contacting the manufacturer (HP) I learned that the motherboard can be upgraded for a higher spec model that does have more video ram.
 
That last part is significant if you are thinking to upgrade your laptop to Windows Vista, because 128MB video ram is what Vista needs for the new GUI. If your RAM, CPU and other laptop specs are enough to run Vista but your machine has only 64MB of video memory, getting a higher spec motherboard may indeed let you upgrade to the newer OS and extend the usefulness of your machine even further.
 
Even when looking at the price of such an upgrade, spending $400 on a new laptop motherboard is much cheaper than throwing out $2000 on an entire new system.
 
I have already upgraded my laptop's RAM, hard drive and optical drive - getting a fresh motherboard would then allow me to install Windows Vista and also take advantage of future Vista software.
 
As is the case with every laptop, check into it - something that you may think is a throwaway item may in fact be more useful than it looks.

One thing the article didn't mention was the Mini-PCI card that a lot of laptops do have. These usually carry the Wireless LAN Cards we all know and love.  
 
On my Sony PCG-R600HFPD I've replaced the original 802.11b card with a 802.11a/b/g card. It's also possible to get cards with wireless internet and bluetooth onboard.
 
Cheers,
Al

Yup, I replaced my Gateway's original mini-PCI ORiNOCO 802.11b WLAn card with an Intel 2945ABG mini-PCI card as well. The 2945 is the fastest mini-PCI WLAN card made as newer 802.11-draft-n cards are mini-PCI-Express like Intel's 4xxxGN WLAN card they'll roll out with their 800 MHz FSB Core 2 Duo CPUs shortly.

I was just wondering if anyone here knows how possible it is to upgrade a Celeron 'M' CPU to pentium 'M' centrino stylez.
 
I have a sattelite pro m40 with a 1.4 GHz  Celeron 'M' chip. Its FSB runs at 400MHz and I have seen clearly that this model is available with up to at least a 1.7 GHz Celeron 'M'.  
 
Now, correct me if I'm wrong, but this SURELY means that the if I try a pentium 'M' 745 1.8 GHz running on a 400MHz FSB the bios clock multiplier should be able to manage at least the 1.7 of the other celeron I mentioned, and would not require a FSB clock speed change. Also the cpu is easily accessible physically. I have already checked.
 
Additionally the heat dissapation for the Centrinos is known to be minimal, maybe better than a celeron chip. so overheating should not be a problem.  
 
This should boost the performance notably due to the huge 2 Meg CACHE and the high clock cycle efficiency that "dothan" cores are renowned for.
 
So I suppose the question is ... am I missing something? are there additional features that the bios must recognise in order to run this cpu (voltages, SSE/MMX style stuff, anything)?  
 
Thanks for your help (if given)

you would have to try it; I don't think the problem will come from heat dissipation nor from voltage, but I'm pretty sure there will be trouble with the BIOS.
My advice: try to upgrade such pieces only when a model has actually been seen with said piece - as in, if you've seen a Satellite pro m with a 1.8 Pentium M, then it will probably work. If not, then it's 50-50.

I bought a pentium m 745 cpu off of ebay and IT works like a dream. A simple swap out for my toshiba satellite pro m40. Performance ULTRABOOST.
 
Legendary VALUE.  
 
p.s. can anyone tell I'm well gald I didn't waste £60

Another think that is replaceable is the power connector port. If you know how to take your laptop apart and if you are fairly good at soldering it is no problem at all to change this. It can bring new life to otherwise doomed laptops. The new ports can be found in a lot of online laptop repair shops.
 
Another thing is the cooling. A lot of pages offers new cpu or system fans for different laptops. They are easy to change and usually they have a parts number on the wire, so you are sure to get the right part. I have also considered buying external cooling as the Zalman device, where you have a plate with some fans under that blows cold air on the bottom of the laptop. If you laptop is easily overheated you could consider this.

A easy How to guide is Upgrading and Repairing Laptops second edtion by Scott Mueller.  
 
I Payed for a Alienware area 51 5550I core 2 t7600 2.33 ghz with 512mb of ram and a low end 60gb hard disk.  Other then a Faulty Motherboard.  They replaced.
 
Now it a Core 2 2.33 ghz.  With 2gb of ram and 250gb hard disk.  Looking into upgrading the grapics card and Up the ram to 4gb of ram. When prices drop on the 200gb 7200 rpm hard drive with 16mb cache and vista seems more stable I will upgrade and drop windows xp pro.
 
Most of the time you can type in the Make of a laptop on notebookreview.com and they will tell you what can be upgraded.