amd64 or i386? VirtualBox can't start client VM

view full story

http://unix.stackexchange.com – My Debian kernel is linux-image-2.6.32-5-amd64, and the command uname -m returns x86_64. However, apt-get do get i386 packages (those /var/cache/apt/archives/*_i386.deb), but never get amd64 package. I want to install virtualbox, but neither -i386 nor -amd64 work for me. I have tried to install virtualbox-4.1-amd64.deb, but it was said the version incorrect, then, I can only install virtualbox-4.1-i386.deb. But after installed -i386, virtualbox couldn't launch the client VM, system mismatch error. I'm confused what the true arch type my system indeed is, i386? amd64? or x86_64? (HowTos)