Building my own Computer for the first time?

The Corsair memory is better and faster, but overall the difference to your computer's performance won't be mive. It would make more difference if you bought a Phenom processor though. Also the HD5770 is ok but isn't the most powerful card available at a reasonable price. If you can stretch to an NVidia GTX460 or a Radeon HD6870 then your graphics will perform much better. You would be fine with a 600W PSU. One more thing, unless you've found a bargain then the price that you show for Windows 7 looks to me like the price of the upgrade version, not the full version which costs about �110. Unless you have a legitimate copy of Vista to install first then you can't use the upgrade version.