There is a user that runs Pluto on a AMD Athlon 64 processor just fine. He didn't have any trouble as far as I know with the installation.
Even when installing with the 2.4 kernel, if everything goes as planned, after the second reboot you should be booting with 2.6, although some manual changes would probably need to be made to the bootloader configuration file, fstab and others. I would point you to another topic that had this solution, but I can' find it..