Is this good gaming? Intel Core i5-2400S Quad-Core Processor 2.5 GHz 4

No. It's not 'good'. It says 'barebones' and it means barebones. It's enough to be functional, but is not really what I'd call a 'good' PC. Especially if you're looking to play games.

It has integrated graphics, which isn't good for a gaming PC. You want a separate dedicated GPU and CPU and at least a couple of PCIe slots for upgrading later. The CPU is also a little underpowered. For a gaming rig you want at least a 2.7 ghz quad core. The Power supply is sub standard. It doesn't have an HDMI out either meaning you'll either need a VGA or DVI. It also has no hard drive and does not come with an OS, meaning you'll have to buy and install your own copy of Windows.

It won't run BF 3. The integrated graphics isn't good enough.

It's an underpowered computer and no good for gaming.

It might make a good starter for upgrading. It has PCIe slots for a GPU, the Ram is decent, and it's got a good slot for replacing the CPU. You'll also need to replace the PSU and cooling as well as getting a hard drive for it.

You might as well just build a computer yourself considering you'll pretty much have to replace or buy everything but the motherboard and case.

Do not buy.

As Contrabardos says, that is far from a complete system. The CPU is OK but for gaming you will need a muscular GPU which in turn will require another PSU. If you add to that all the other hardware that is missing plus the OS, you probably have to add $500+ before that will become an entry level gaming rig - and I even doubt that the base lends itself to all the required upgrades.

You do better if you start from scratch with a good size box and the right bits. If you want to start with a kit, look at TigerDirect. They often offer kits at good prices that would make a better base. But don't kid yourself about price. A halfway decent gaming rig will run at least $1000 to $1500.

For a buget of $400 it is not worth building a PC. It is cheaper to buy one - especially tomorrow and Friday. But that will not be a gaming rig. The best you can play on a $400 PC is hearts or chess.

A bare bones system is intended to be only a starting point. It has a case, PSU, motherboard, CPU, and cheap RAM. That one is two generations behind current tech as well. You'd need a CPU cooler, case fans, possibly a CD/DVD drive, OS, etc to become a system.

Personally if there is just $400 to work with I also would buy a pre-built one, at least you'd have up to date tech to work with. As WHS said, tomorrow and Friday (28th and 28th NOV) would be a good time to shop, but you'll have to be quick.

Britton30 said:

A bare bones system is intended to be only a starting point. It has a case, PSU, motherboard, CPU, and cheap RAM. That one is two generations behind current tech as well. You'd need a CPU cooler, case fans, possibly a CD/DVD drive, OS, etc to become a system.

Personally if there is just $400 to work with I also would buy a pre-built one, at least you'd have up to date tech to work with. As WHS said, tomorrow and Friday (28th and 28th NOV) would be a good time to shop, but you'll have to be quick.

And since he wants to run BF3 and alike, he'll need a pretty good GPU and a beefy PSU which alone will cost a good penny.

Here's a list from Newegg.
Newegg.com - PCs & Laptops, Desktop PCs, All Desktop PCs

This one may work for light gaming for $499. But you have to hurry - it is a black Friday special.

Newegg.com - CyberpowerPC AMD FX-Series 8GB DDR3 500GB HDD Capacity Desktop PC Windows 8.1 64-bit Gamer Ultra 2175

You're welcome and happy black Friday madness.