I have a box already has openSuse 11 32bits installed. I want to replace it with openSuse 11 64 bits. When I insert the openSuse 11 64 bits CD, I got error message "this is a 32 bit computer. Can not use 64 bit software".

so How do I wipe out the old OS (32 bits), and install new OS (64 bits)?

Thanks!

This error message has nothing to do with the fact that there is already a 32 bit OS on your system. This error message simply means that your system is not capable of running a 64 bit OS.

Moved to Suse/Novell as this isn't a security issue.

So the 32 bits is not related to the OS, but the computer hardware?

It is both. If you want to install a system on a computer, it will, at first, not care about an already installed system, may it be 32 or 64 bit.
But before starting the installer it has to load a kernel, and this kernel will only run on architectures that it supports. In your case the 64 bit kernel recognises that your CPU is "only" a 32 bit CPU and therefore belongs not to the kernel's supported architectures. This is what the kernel reports to you.

So if you really want to run a 64 bit OS, there are only two options for you:
1. Upgrade your hardware.
2. Run the 64 bit OS inside Virtualbox.

Virtualbox won't run a 64 bit OS on 32 bit hardware. If the processor is 32 bit, that's the end of the story.

You can run a 32 bit OS on 64 bit hardware using a legacy mode in the hardware, but you can't do it the other way around.

Then you have to say that to my Virtualbox. It does the impossible and runs 64 bit-systems on a 32-bit host just fine.
http://img254.imageshack.us/img254/2615/64on32.png

Then you have 64 bit hardware.

Actually, your sig says AMD 1055. What do you think that is??????