See this link
and this link
for more information on this issue. BTW, I googled "ubuntu 10.10 bios nx capability" and saw a boat load of hits on this issue so if these don't help, try some of the other results.
The short answer is that there does not appear to be a way for (most) to enable this feature in the BIOS. The work around is the following command:
sudo rm /etc/update-motd.d/20-cpu-checker
The catch-22 being that I think you need to have the system running to use this command. Can you launch a root-recovery shell (from the grub menu) and try the command that way?