Sometimes changing the lights to CFLs will not be enough. Changing the lightings to high efficiency & high output LED lighting would be the solution (at least for the lighting side of the problem).

As for using a PC, a standard PC is wasteful of energy. A net-top PC or even a netbook would conserve power while still giving you access to the internet, etc. (Of course if you want to play graphics heavy games, there is no choice but to use a more powerful PC).