Linux 32-bit and 64-bit distributions:

PAY ATTENTION:
==============

Even if your machine runs a 64-bit CPU (AMD, Intel Core2), you must install 
a 64-bit kernel to run 64-bit applications, otherwise you will NOT be able 
to run 64-bit applications.

For instance, Fedora distro Fedora-9-x86_64-DVD.iso will install a 64-bit kernel
when          Fedora distro Fedora-9-i386-DVD.iso   will install a 32-bit kernel !!


To find out if you run a 32 or 64-bit kernel:
==============================================

$ grep CPU /var/log/dmesg
CPU0: AMD Athlon(tm) 64 X2 Dual Core Processor 3400+ stepping 02
$ uname -m
i686 
         ==> This is a 32-bit kernel installed on a 64-bit CPU
         ==> you can only run 32-bit applications 


$ grep CPU /var/log/dmesg
CPU: Processor Core ID: 1
CPU1: Thermal monitoring enabled (TM1)
Intel(R) Core(TM)2 Duo CPU     E6550  @ 2.33GHz stepping 0b
$ uname -m
x86_64 
         ==> This is a 64-bit kernel installed on a 64-bit CPU
         ==> you can run both 32 or 64-bit applications