My little Macbook is about 6 years old now and I can't really justify its replacement yet, as it looks good and works pretty well, compared to ordinary PC laptops of its age. The performance of the Intel Core2 Duo 2.0 GHz (T7200) is quite enough for me in a secondary computer, the RAM could be faster (and bigger) and of course laptop HDDs are painfully slow, so there is room for improvement. It's hardly breaking news that you can fix some of these things with a little investment; I went a bit further in the process of modernizing.
What you see here is a 120GB Adata SSD, a hard disk caddy with the 500GB HDD that I put into my laptop years ago, 3GB RAM (the maximum this Macbook can handle), new CPU cooling fan, thermal paste, a new battery and an external optical drive. The "Superdrive" was about to die, so it was a good decision to replace it with a secondary HDD and the original battery was bent out of shape by now. It's best to follow these iFixit guides using proper tools, like the iFixit Pro Tech Toolkit that I ordered last year and I've been using it happily ever since. It's totally worth the money, especially for the ultimate screwdriver collection with 54 different bits.
After successfully taking off the top case (keyboard + touchpad), I took out the CPU cooler and the Superdrive and took off the heatsink to clean it, along with the CPU and the motherboard controller chip's surface, so I could add a fresh splash of thermal paste on them to improve cooling performance. The cooler itself wasn't in a too bad shape, but it's worth to get a new one on the cheap. The hard disk adapter is similarly cheap, you just have to keep in mind that this Macbook uses an IDE connector for the optical drive, so you need this one which converts SATA to IDE. Installing it is a bit harder, there are some rails and sticky stuff that you have to peel off the optical drive and put it on the caddy, to the same position, especially the Bluetooth antenna holder due to its limited cable length. Installing a primary SSD and RAM extension is easy, you don't have to take the laptop apart for that.
After it was all done and I put back all the parts, cables and screws, everything worked well for the first try. Well, except for the cheapo external DVD (18 bucks) that fails to work most of the time and I can't boot from any disc with it, no matter what I do. It's really a piece of junk, I won't return it only because mailing it back would cost half as much as the drive itself. I'll get a properly working optical drive when I really need it, luckily I already installed Windows 7 on the SSD (added it separately last year) and there was a Mac OS X 10.7 partition on the HDD, so these will work just fine for now. I bought a second Windows 8 Pro license that I could put onto the Macbook, but I don't think it's worth doing so, and it's good to have a Windows 7 machine around for testing.