<p>A sub-$600 laptop for four years is a bit of a stretch. I would have to recommend a thinkpad, either an Edge (more like a netbook) or an R series (will be a bit underpowered compared to a T). I have also read good things about the new X100e. The performance won’t be great, but you can always drop Windows and install a light Linux distro. If you aren’t comfortable with Linux, I would recommend Ubuntu. If you have previous experience, you can probably get the best results with Arch Linux (complicated).</p>
<p>For under $600, your only options are going to be a high powered netbook or an underpowered notebook. Battery life is probably one of your biggest concerns if you plan to use it to take notes, so I would recommend leaning towards a smaller screen and an Atom processor. If you can, try and type on whatever you choose before you buy it. Some of the smaller keyboards are completely unusable if you have larger hands. Really though, you should look around and find something you like before making a decision.</p>