Project Apteros - The First Day

When I last upgraded my computer I was left with alot of spare parts, almost enough to build another. This is a wonderful chance to build myself a crash test pc, sort of like a spiritual successor to Alge. First off I'll be running Ubuntu on it, as it seems really wonderful, and I don't want to go through any trouble with my primary computer, due to all the stuff I've got on it.

What I need is the following:

• Ram (Borrowing 256mb pc2100 of a mate) Can run PC1600, 2100 and 2700.
• Hard Drive (I've got an ancient 3gb one plugged in now, but not sure if it works)
• CD-Rom
• Power Supply (How do I know what kind I need? Does 230w still do the trick?)

So a mate came over today, bringing some ram, an old hard drive (which we found out was broken), a CD-Rom and a Power Supply (230w). We set the computer up and started it up with an Ubuntu disc. Halfway in the loading screen the computer restarted. Then it did again. For a long time we believed it could be a faulty disc, but then I tried a boot without the CD, and it still restarted randomly. I have no idea what the problem can be, and any feedback would be wonderful.

We couldn't get much further because I had to go to work. Part II has no set date yet.