Thanks for the reply. It turned out that the installed SMP kernel wasn't the default kernel so I had to edit grub.
Unfortunately, neither the 2.6.8-2-686-SMP nor 2.6.8-3-686-SMP will boot.
2.6.8-2-686-SMP chokes on installation and then when booting can't mount root fs on unknown block(0,0)
as per this thread:
2.6.8-3-686-SMP installed fine and starts to boot but then hangs up with this inode wierdness I'm still trying to solve:
Those appear to be the only two 2.6.8-SMP kernels for Sarge,,, wondering if I should try a more recent kernel from Etch or not.