Originally Posted by Dims
I have installed Debian Lenny from the distribution and have choosed "amd64" version.
What does it mean? It concerns only kernel or everything?
It means you have a 64-bit kernel that can support 64-bit applications. ("AMD64" does not
mean it is only for AMD CPUs. "AMD64" is the same as "X86-64" and is for most Intel 64 bit CPUs as well).
It tends to mean everything, not just the kernel.
You can run 32-bit applications under a 64-bit kernel. But installing them may be tricky. Since you have a 64-bit kernel, the package management software (normal method of installing applications) will choose the 64-bit version whenever it is available (which is almost always).
Having this system installed, can I turn amd64 back off without reinstalling it? Is kernell recompilation is sufficient?
No. To switch from 64-bit to 32-bit, you would need to reinstall the whole distribution, not just the kernel.