Is this a good "gaming" computer I'm buying?

I'm planning on buying this computer. It's a computer that's over clocked to 3.9 GHz. I plan on getting it the way its set up except I'm changing the Ram to 4GB instead of the default 2GB. I play to mostly play games on it...and yes...I know its not a good gaming computer...if you even want to call it a gaming computer. I DON'T plan on playing Crysis 2 on ultra high...geez. I mostly want to play games like Red Alert 3, Starcraft 2, Modern Warfare 2 (maybe), Oblivion, ect. I am ok with playing these games even on very low. I've played Red Alert 3 for two years on my parents computer on very low and yes...I was okay with it. I just want to know if this computer is "good" and could play these games...if I could play these games on medium I'd be more than happy. I have $450 and this is in my price range. I plan on upgrading the graphics card to a "GeForce GTS 450" if possible when I get enough money because I'm broke now. And, I also know that this doesn't have a Operating System or a monitor. I can get Windows 7 from a friend and I have a monitor. So I want to know if this could play these games or could play games and if this is a good deal or if you could find me something slightly better. That's about it...PLEASE DON'T say, "this computer is complete crap!" or, "with $100-200 you could get something wayyyy better". So please respond, thanks. ^^