Installing Kubuntu 12.04 On Older Non-PAE Computers

Many users interested in trying out the latest and greatest Kubuntu (12.04 Beta 2 as of this writing) on older hardware have found out that the .iso images provided for download will not run on their computers. If you are one of these unlucky people, you will see a message on boot stating: "This kernel requires the following features not present on the CPU: pae
Unable to boot - please use a kernel appropriate for your CPU."

Physical Address Extension (PAE) is a feature to allow (32-bit) x86 processors to access a physical address space (including random access memory and memory mapped devices) larger than 4 gigabytes (Wikipedia). The decision to not include non-PAE  complaint  computers for a 5-year  LTS release is understandable as this group would include all Pentium M-class processors and older, and 5 years is a long time. While it remains to be seen whether Canonical will make available final release images that are tagged "non-PAE", you can install Kubuntu 12.04 on these older machines by using the "non-PAE mini.iso" CD/USB image to initiate your installation. Weighing in at a slim 24MB, the mini.iso also has the advantage of allowing a very customized installation of your fresh new Kubuntu system.

Once the image is loaded, it basically act the same as the Alternate Install  image, offering a text-only install without the GUI installer many are used to. Be warned, however, that since only the bare-minimum is put on the image, everything will need to be downloaded from the web, including the Ubuntu base system and all KDE / Kubuntu related packages. This may be problematic for users on slow internet connections. Even with a fast connection, this method will take time do to the sheer amount of data needed to be downloaded and installed.

The non-PAE mini iso images for 32-bit processors can be found here.

Lastly, it should also be noted that current 10.04 and 11.10 users can upgrade their systems per the instructions on the Kubuntu Beta announcement page, as upgrading an existing installation on non-PAE systems will allow the distribution upgrade to take place while installing the correct kernel.