Lenovo does not offer any overclocking utilities. You'd need to repalce the CPU, check your model on lenovo's web site and see what it will run on.
You may also want to look into a RAM upgrade if you are at 1gig or less, or a Windows re-installation.
That CPU is not bad, why are you trying to upgade it? I can pretty much guarantee the CPU is not at fault for whatever slowness you are seeing.