you normally cannot overclock if you have the standard intel
mobo installed.
For lappies 
, you first need to have a
separate mobo, like gigabyte, MSI, etc...which includes the
suitable bios for overclocking...
Then you can overclock, even the GPU speed, memory speed etc, not
just the CPU speed.
Also you can also dynamically overclock if you have a suitable
software where you can click in windows, instead of changing at the
bios.
And, for laptops as of now, at most you can do is the intel speed
step or something, or power settings...
where let's say your Intel Centrino etc, is 1.7Ghz but showing only
900mhz or 1.1ghz etc at the properties, you may reset your power
setting to maximise it to the full speed at 1.7ghz. 
