Like the others said, your Pentium isn't all that bad. Its basically an i3 without hyperthreading, which doesn't help much in games.
The GTX 550Ti is an OK entry level graphics card.
Most games don't really care which CPU you have, as long as it is at least dual core and like 2.5 GHz. Its mostly about the GPU. There are some exceptions, but your CPU should be fine for the time being.