Fixing the DRE

K, so here's the deal: I want a PS2. My friend has an extra PS2 that gets the DRE that he hasn't been able to fix. He said that he'd give it to me, and if I could get it working, he'd sell it to me cheap.

So I wanna know the best ways to fix it. I don't know what model it is, but I do know that he's tried this method without success. That basically comes out to his warranty being voided and a chance that me trying the same thing not working.

Does anyone else know of a good way to fix it, or have experience with fixing the DRE?

I used to get the DRE on the games with the blue CD bottoms. I just stood my PS2 up vertically and the DRE went away... not really sure why. When I put it back flat, the DRE comes back. So maybe you can try that... though maybe I'm just lucky. If the solution was that simple, then everyone would know it by now.