So much of this you may already know, but here is a rundown that will hopefully aid you in understanding all the junk that people posted on your thread (good junk).
The basic parts that you need to get your PC running are the following: CPU(processor), GPU (graphics card), motherboard, RAM, hard drive (with an OS installed),Power supply, CD/DVD drive and of course, a case.
To understand what all of those do, lets look at the build I sent your way and consider each part.
Phenom x4 960T: This is an AMD quad core CPU. This means that it can run four simultaneous streams of information, obviously increasing efficiency and speed. Nowadays it is pretty standard to be getting a quad core CPU, despite the fact that many games still only run on two cores. Nevertheless, it is good for many other applications. This particular CPU is unique in that it can unlock to a six core. The story behind this is a bit complicated, but just know that AMD maked 6 and 8 core CPUs as well, and when the chip isn’t quite up to spec they disable two cores (on the x6) and sell it as a quad core. If you have the right hardware you can actually unlock those extra two cores on some. For your purposes you will not need it, but it is cool nonetheless.
XFX 6850 Black edition 1GB DDR5: This is your GPU, the main source for performance in many games you will be playing. It can be debated whether or not a game relies more on the CPU or the GPU but the fact remains that you need to have a good graphics foundation to have a good gaming experience. This particular card is right in the middle as far as performance goes. It is “last gen”, as the new 7xxx series is out, but you will not be missing much. This card supports Directx 11, the future of gaming processing, so it is a good choice to have for the next while. It will not max out every game out there but it will play everything well and be a good place to start
Asus Saber Tooth 990 FX: This is your motherboard. We could go on for a while on different chipsets and all, but you should really do research on your own into the finer points of a good motherboard (crossfire, SLI, VRMs, heatsinks, # of sata ports, etc).
Cool Max 600w: Your power supply. This determines how many of what type of components you can have running in your system. If you have a lower rated power supply and you put too much into the system, you run the risk of frying your parts. 600w is PLENTY for this build, with room to add other components. There are useful tools online to determine the size power supply you need for your system, though they tend to overestimate the size you will need, as they are trying to sell you the part!
8GB of G.Skill DDR3 RAM: Here is your RAM (duh). This stands for “random access memory”. You will notice you cant multitask on your netbook very well partially due to the fact that you have very little ram in the system. 8gb is considered more than adequate for gaming needs these days. As you get more experienced you will learn about RAM speeds and timings, but for now you should learn the good brands from the not so good brands and which place nice with AMD or Intel CPUs.
Wireless PCI netgear N adapter: This is a handy addition for wireless connectivity to the internet, but as you are going to be gaming, I would recommend a hard wired connection (Ethernet cable to router/modem)
Cooler Master Elite 311 Case: The home for all your parts! Cases vary in all shapes, sizes and function, so just find the one that works for you. I have a decent case with really good airflow (fans placed in the right area keep your parts cool and working). Cooler Master tends to make really nice cases, so this is nice.
Hard drive: This is where things can get tricky as well. You mentioned not needing a whole lot of space on the drive, which is great, but I still wouldn’t recommend going for anything less than 500gb. You would be surprised how fast it fills up with stuff that you use frequently. Right now, as was mentioned, hard drives are rather expensive due to flooding of manufacturing areas, so I would steer you toward the marketplace to find new/refurbs there. People on this site tend to be pretty good with prices and help you with warranties if things go wrong. With hard drives, typically the faster they spin the better (5000rpm, 7200rpm even 10000rpm!) but that isn’t always what you need to look for. The size of the cache and the reliability of the brand bust also be taken into account.
OS: You can get windows from a lot of people on KSL. I got mine from a guy in a business park who had extra keys from a mass buy he did. It came out to be around $40 and worked out really well. Someone else already gave the numbers for a new, retail copy, so there is also that.
I hope this helped! It is pretty simplified and some might correct me on things, but this is the basic info you need to know for your purposes. Welcome to the world of custom computer building! You will NEVER go back, I promise that much.