To check your current cpu speed you can do:
cat /proc/cpuinfo | grep MHz
The grep bit is optional, neatens the result up a bit though
Good thing about c'n'c - less noise from the cpu fan and, I would guess, less electricity consumption
You might need to have a look in your kernel and see if there's anything else that needs to be enabled (or possibly think about about trying a more recent kernel, see if that helps).
I use 'speedfreq' to dynamically change cpu speed as 'powernowd' stopped working on my computer as of kernel 2.6.11