Good to hear that. Under knoppix probably you only had to add kernel options (switches) at boot up. This can be easily done right at the boot loader. What bootloader you run? Under Grub 2 switches are given by editting /etc/default/grub; with Grub Legacy much easier editting at /boot/grub/menu.lst. Common options given are NOAPIC, ACPI=OFF, etc, placing it beside the "quiet" switch. If your kernel is equipped with MODESET for graphic card auto mode (resolution) setting this often causes the system to hang right the inception of X loading; this usually needs switching NOMODESET at Grub so that kernel will not contend against, rather, peacefully delivering to X the role of fixing display resolution.
A matter to share: I too had to undergo similar indigestions installing Gnu-linux in older hardware. However, without denoting anything to Knopix (this is also a fine distro), my experience had always landed me to Absolute Linux
which always solved everything for backward hardware. There is also Antix for backward hardware compatibility.
Hope that helps a bit.