Dell Dimension quandary

I have a Dell Dimension 4550, P IV, 512 MB RAM, nvidia card. I have tried to run several different knoppix live CD versions, using just about every cheat code including failsafe, with no success.

However, recently I have been able to run the Slax and the Dyne:bolic live CDs with absolutely no problem - no cheat codes.

I prefer to run the knoppix versions, which I do readily on my Sony notebook. Does anyone know of a reason why I'm having so much difficulty with the Dell Dimension 4550.

Thanks

Do you have more information about that computer? Whch harddisks does it use? Which soundcard? And what are the error messages you get when booting? (If you don't get any, have patience and wait a bit longer...)