Thanks going there to check things out.
PaulT

PTabolinsky,
400w is a bit of overkill, each system probably draws less than 200w. But it's never a good thing to run a power supply at 100% 24/7. It will shorten it's life and produce voltage fluctuation. Besides, each system will only draw the power it needs and the power supply will only supply what is demanded of it. No electricity is wasted by using a slightly larger power supply.

I used Fortron/Sparkle units with a 120mm fan so they run nice and cool and quiet. Plus they are a very well built power supply and will last for many years. I can buy them new for under $40 Canadian each so cutting costs in this area didn't seem like a good idea.

512MB of RAM is more than enough for a cruncher, even a dual core. You can disable all the useless stuff in XP and cut it's RAM usage down to under 100MB. That leaves over 400MB for crunching. There are only 2 reasons to add more RAM: 1)you want to run HDC which requires 768MB or 2)you want to run the RAM in dual channel which will net you about as much speed as adding a RAID 0 hard drive array. (ie: nothing).

=PiA=
Yep, strictly crunchers. I had enough parts lying around to put together 2 of them. The rest I collected over several months during online blow-out sales, buying used parts, etc. I probably couldn't buy a descent off-the-shelf machine for what I spent on this. I don't give to charity very often so this is my way of doing that. Plus I can write off the parts and electricity through my business so it's not costing me much at all. I'm very passionate about grid computing for the benefit of mankind so I do what I can to help out.