PCs + water -- why?

The main reason that I want to have an unusual cooling mechanism on my PC is that I want to overclock it.  In fact, I want to overclock it a lot.  I do not, however, want to have a very hot PC.  The air flow inside my PC is not wonderful -- it's enough for the large heatsink that there presently is, but I have some upgrades in mind that may make the present cooling insufficient.  I want an internal Zip drive, which will mean I have another ribbon cable fouling the interior, and I want to get a Riva TNT based video card, which will also get hot.  I will, in time, add another hard disk too.  All these things heat up the case.

So, to counteract the fairly laden and overclocked PC, I will need some means of keeping it cooled.  The normal means of doing this is to use a heatsink with one or more fans attached to it.  However, like I mentioned, I don't think that the airflow inside my case is up to that.  I want a means of getting the heat from the processor to outside the case, where it can be dissipated more easily, without heating up all the other parts of my PC.  This means that I will have to use some form of water cooling.

As water coolers for PCs don't seem to be readily available, I will have to build my own.

I may also devise some cunning cooler for my video card, and anything else that looks a bit warm.