'Gaming' covers a huge range of possibilities. The i7 is a good processor (possibly overkill - many gamers find the i5 good enough) and the GTX750 is decent mid-range graphics card that will give you a reasonably good experience on most modern games. Does that price include the operating system? I'm assuming yes. Compare it with this: I know nothing about the seller, and it doesn't include the operating system, and the processor isn't as good as the i7 (but probably good enough) - but it's considerably cheaper. That said, it's worth paying something of a premium for llocal support in the vent things go wrong. I've bought from ViBox and been very satisfied - again, no operating system, but a very decent processor, and quite a bit cheaper. This is refurbished, but it's a Dell - and it does include W7. (I find Dells harder to upgrade, though, than regular custom-built systems.) In summary: it's a reasonably good PC, will give you a pretty good gaming experience, and, if it includes the operating system, you may feel more comfortable buying from a local company. But: you can buy cheaper - or better for the money.
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