Just one more generic comment about the x86_64 architecture. This architecture supports the identical 32-bit architecture expected by 32-bit code. Programs built as 32-bit will think they are on a 32-bit x86 architecture. gaf@gaflap:~/src> gcc hello.c -o hello64 gaf@gaflap:~/src> file hello64 hello64: ELF 64-bit LSB executable, AMD x86-64, version 1 (SYSV), for GNU/Linux 2.4.1, dynamically linked (uses shared libs), not stripped gaf@gaflap:~/src> gcc -m32 hello.c -o hello32 gaf@gaflap:~/src> file hello32 hello32: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.2.5, dynamically linked (uses shared libs), not stripped Another issue is the OS. You can run either a 32-bit or a 64-bit OS. he 32-bit OS will not give you any of the additional features of the 64-bit architecture. A 64-bit OS runs in full 64-bit mode, but does allow both 64-bit and 32-bit binaries to run. -- Jerry Feldman <gaf@blu.org> Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9