Quote Originally Posted by mepouze View Post
It's impossible to boot on it because my priority device is hard drive first.
I've disabled cd priority.
This problem is inside Centos wich has been, according to me, modified somewhere by knoppix.
Knoppix will use a Linux swap file if one is available on the hard disk. Beyond that it should not write to the hard disk at all unless instructed to, and even then there are several safeguards that make writing (accidentally or deliberately) hard for a beginner. Ive seen a few other cases where someone claimed that Knoppix mucked something up on its own, but have never seen a confirmed case of it.

I assume it was possible to boot Knoppix at one point, otherwise you likely would not claim that Knoppix made a change. And it would be "possible" again, just by the flipping the BIOS setting again. Why disable CD booting (or CD priority as you call it) when you could prevent booting a disc just by removing it from the drive?