Re:I like D.Net (Score 2)

now I've moved onto the RC5-64 challenge because I have nothing better to do with my spare CPU cycles.

But there are better things you can do with your CPU cycles. There are several actually useful distributed computing projects out there, like the protein folding project others here have mentioned. Or maybe you would prefer to help dseign new genes. Or surely you could find something you might like.

Personally, I think SETI is pointless

It may be unlikely, but least it is theoretically possible for SETI@Home to produce significant results. However, the RC5-64 is guarenteed not to produce any useful (or even interesting) results. It will teach us nothing we don't know already.

it doesn't hurt me at all that if my machine happens to find the key that I get $2000

If you want a shot at winning a prize, you could try looking for huge prime numbers. While that doesn't seem to be particulary useful, at least the money is better. And more importantly, you won't spend years searching for something we already know.