Boot problem: stopped at start X

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Knoppix live CD 5.0.1 boot stopped at the start-X logo graph. It is very strange that sometimes the CD can boot normally in my computer, and sometimes can not.
My computer is Pentium 4 and Intel845 chipset. The DVD can be recognized as hdb, and the harddisk is hdc. I am sure the problem is not burning CD problems, because I have installed the Knoppix 5.0.1 in the HD, and it still sometimes stopped at start-X and sometimes boot normally.
Can anybody give me some suggestion? Thank you in advance.

[ockham23]

Your drive setup looks strange. Normally, the hard drive is attached to the primary IDE channel (IDE0) and jumpered "master". Linux will recognize it as "hda". Your DVD drive should be "hdc", i.e. master drive on the secondary IDE channel (IDE1).

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Thank you for your advice.
I changed the IDE connection but the problem still remains. Now the DVD is hdc and HD is hda.