What makes you think that increasing the amount of power you supply to your laptop is supposed to make it run faster?
I think that there's a minimum, below which if laptop is not getting sufficient power, it might run in a power-saving mode, which means CPU will not run at full speed, so it might seem slow as a result. But 90W for laptop sounds like plenty, considering average laptop requires like 65W adapter, so I doubt your laptop is not getting enough juice.
To speed up your computer, first check if you have any viruses (if you paid $200 for a quad-core laptop, something tells me you bought it used, and if so - previous owner could have it infected). Secondly, disable any programs that you don't want to be running. At this point, you should see some definite improvements in speed. If it still feels slow, maybe Windows needs a clean reinstall. Finally, if even after reinstall everything seems slow, it may indicate a hardware issue (possibly failing harddrive), or you may want to add more RAM to the laptop, or replace harddrive with SSD. Whatever the case, i7 720qm, despite being a few years old, should easily handle pretty heavy loads (unless, of course, you're trying to play graphics-intensive games on it, and the laptop has a weak videocard, like an integraded one).
