Why does my server boot the old debian kernel?

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http://serverfault.com – I got a vServer with Debian installed (important because I have no idea of how Debian was installed and/or built). Output of ~# uname -r: 2.6.26-2-xen-amd64. After execution of (first some other version 3.2 kernel installations and then) ~# apt-get install xen-linux-system-3.2.0-4-amd64 and preceding ~# update-grub and ~# reboot the kernel version seems to be unchanged. Why? ~# dpkg -l | grep xen gives (reformatted): libxen-4.1 (4.1.4-2) libxenstore3.0 (4.1.4-2) xen-hypervisor-4.1-amd64 (4.1.4-2) xen-linux-system-3.2.0-4-amd64 (3.2.35-2) xen-system-amd64 (4.1.4-2) xen-utils-4.1 (4.1.4-2) xe (HowTos)