In an excerpt from the newly published book Linux Live CDs, Linux.com describes how you can start up PK on multiple nodes to run a cluster, and customize PK to add or remove applications.
Read it here
To start PK, power on the computer with the CD in place. At the boot screen, just press Enter, unless you need to pass boot options to the kernel to get it to boot. For example, you might want to pass the acpi=no argument to the kernel if you have had problems getting PK (or other live CDs) to boot.
After ParallelKnoppix has started, you might notice that it seems to be missing the menu bar. Actually, ParallelKnoppix has a taskbar, but it's hidden. Move the mouse to the bottom of the screen, and you'll see the taskbar after it unhides. If this behavior annoys you as much as it does me, right-click the taskbar and select Configure Panel. Then you'll see the Configure KDE Panel dialog, and on the left side you'll see Hiding. Click that and deselect Hide Automatically under Hide Mode.