Is this a good custom computor?

Nice processor. Although you might want to consider waiting for Nehalem, it will be more expensive but if you have the money the previews look GREAT for it, and it is supposed to launch in september. That ram, if you are overclocking you might want to go a step higher (i think 1033? unless you can get the memory divider to work around 800, but for stability's sake it might be safer going with 1033). The hard drives, you really would be better off getting one of those high speed drives (i think the western digital velociraptor is a good one) as many people have shown for gaming it does not significantly impact gameplay (perhaps shorter loading times, but you can also run into some major problems with raid 0). That video card (sorry to say) is pretty much trash, go for something in this generation if you are getting a Q9450 (the 4870x2 is coming out soon, it is DEFINITELY worth waiting for). Everything else looks good except for the keyboard and mouse, you might want to get something else more suited for games (logitech g5/g9, microsoft sidewinder, etc).