While it is good to see DYI laptops, the article is Published on August 1, 2008 and Updated on May 1, 2015. Glancing at the technology involved its all appears to be from over 5 years ago.

Recycling centres may sell you a laptop with, say, a broken screen and/or some smashed keys for $20 to $40.
Inside it, you may get:
> 2GB Ram,
>= 160GB Sata 2.5 inch disk drive
Mini-PCI Express (PCIe) Wifi
Removable CPU and GPU chips.
A good screen that can be used to replace a broken one.
A battery which might last 10 minutes.

If you shop around re-cycling centres, then over time, you may be able to buy 3 x broken laptops for less than a total of $100 and be able to build one good laptop that matches the sort of specs described in this article. Note: This doesn't account for your labour and driving around time and costs.

If you then spend $100 on a new SSD sata drive, that should help with performance, and you'll have a pretty good DYI laptop.

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On a similar DYI theme...  

What I've noticed in secondary school IT labs is 240VAC desktop units and monitors connected to a main server by wired ethernet. They require an air-conditioned room to dissipate the heat for the 30 x desktop units, the teachers server and the heat from the students. This configuration involves high costs in initial classroom re-fit and wiring installation, high cost of initial IT hardware, high power consumption to run the lab, and (in theory) the high cost of the proprietary operating system and software products.

My DYI for an IT lab would be along these lines...
28 x Raspberry PI 3's that use +5V.
28 x LCD monitors that use +12V with HDMI input and cable.
The RPi's are bolted onto the bottom of the monitors. So the students cant take them home.
4 x rows of desks that can sit 7 students each at their Raspberry PI and monitor.
4 x DC power supplies from old desktop computers - one for each row.
For each row run +5v and +12V for the 7 x RPi3's and 7 x Monitor's in each row.
For each row have a wireless ethernet router for that rows RPi's to connect to. This router will have a 1Gb/s ethernet cable back to a LAN card in the teachers server computer.
28 x wireless keyboards and mice are kept in a lockable cupboard, the students get them out, put them away for each lesson.
28 x breadboard kits with resistors, LED's, etc. are kept in a lockable cupboard, and can be handed out to plug into the RPi's when teaching GPIO port programming, etc.
Each student is responsible to buy and bring to class his/her own micro-SD card that contains Raspbian and their data. (>$10 for 16GB)
Each student is responsible to buy and bring to class his/her own earphones. (>$10, but they have probably already got a set for their mobile phone.)

The teachers server would have 5 x 1Gb/s LAN ports, 1 for each wireless router and 1 for external connection to the schools LAN / Internet.
 
If you allow 5W for the RPi, and 20W for the monitor, then you achieve 25 Watts of energy consumption per student. This is 700 Watts for the classroom (excluding the teachers server).  This may be less than the power consumption of the lighting for the classroom, unless they have already switched to LED lighting. Air-conditioning of the room may be found to be unnecessary.

...Anyone got any design ideas and enhancements?