Hello,
The first time I built a computer, it was back around 2000. Going from memory, I built it on an ASUS (or was it an ABIT?) board with an AMD XP Processor at 1.6GHz and 768MB RAM several optical and hard drives and an (big!) Antec case. It was a workhorse for six years. It could have lasted longer (I think it just needed a CMOS battery - but I was also getting random shutdowns from overheating) and it was still competitive with low to medium desktop systems when I replaced it.
The next (and my current) computer I bought from HP, because I was too busy and lazy (and lacked the motivation) at the time to build it myself. It has a ASUS (nVidia) board and an AMD X2 4600+ with 1GB RAM. It is a good system, but alas, competition for computer time with family members necessitate that I acquire a new computer.
In about a month or two (when I have the money saved up), I am going to build another system - two or three, actually. The first will be on an ASUS or Gigabyte board (not sure if I will go ATI or nVidia) with an AMD X2 4850e and 1-2GB RAM. I am also deciding whether to get a fit-PC or not (it is oh so tempting to give it a try).
The other system (which might have to wait a little bit) will be a mini-itx system. Gigabyte showed off a couple new mini-itx boards last year (I saw one site selling them for $300 - I'll wait for the after holiday sale
) built on the VIA C7 Eden CPU (1.2 - 2.0GHz). There are also JetWay boards built on the same CPU, but I have heard bad things about JetWay. I'll build this with 1GB RAM and in this one I'll definitely put in a CF hard drive (though I'm considering it for the others as well). I'll put all of this into a thin client (hopefully sealed - as in fanless) case.