You need to post some details about your system, motherboard, chipset, sata controller if known.

The hard drive isnt causing the hang, knoppix will boot with no hard drive whatsoever. Heres a list
of boot parameters, more commonly known as cheat codes:

http://www.knoppix.net/wiki/Cheat_Codes

You dont state if any boot messages are being displayed, or the last message displayed on screen.
You may be unlucky and knoppix may not recognise the hard drive controller.

Be aware that knoppix 5.1.1 uses kernel 2.4.19 and knppix 5.3.1 DVD uses a more recent 2.6.24 kernel.
Which version of knoppix are you using?