Assuming a gaming use (which is never a realty safe assumption) your PC looks good.
CPU-OK, as you can see in this ref it's near the top http://www.tomshardware.com/reviews/gaming-cpu-review-overclock,3106-5.html
Memory-OK (4GB fine for games, you could add another 4 cheap, but its not needed)
Verify you have a 64 bit OS before adding memory.
Power Supply - excellent
Video == OK to good, but is your weak link for gaming. GTS450 Here is a ref: http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107.html
your video is currently equal to the $115 cards -- to improve your system you'd need to get a GTX 560 or an HD 6870 or stronger.