My system is situated in an ebay bought case. It's a nice case with a cool lit blue informative LCD display, and if you manage you can stick 6 case fans on it, it's mod friendly, and good except for the room - a wee bit tight in there.

My motherboard is an Abit AV8 guru (I nick named Harrier), processor is an 3800+ 939pin AMD64 clocked 2.450GHz, with a Thermalboost K8 copper heatsink, by ThermalTake.
My choice of thermal paste, being non-conductive and for proper heat transfer from processor to heat sink is Arctic Silver; Arctic alumina premium ceramic paste. Great stuff.
For my sound card, I bought an Audigy 2ZS Gamer Edition for $109.00. Hey, four games and a sound card - for the price you can't beat that!
Now for my baby, I present to you all, a fantastic masterpiece the Leadtek A400 TDH GT, otherwise known as the Nvidia 6800 GT, with it's massive copper cooler in the front and a shiny copper heat sink plate on the back , you say to your self, how cool is it? Well how about 47c idle and I've never been past 58c full load, but it varies on my ambient temp. This card was a nice christmas present from my self for $300 with the help of my best friend.
Here is the rest: A Western Digital SATA 120GB HD, a Mach 8 Pacific Digital DVD R/RW and a floppy drive, but wait there is more!
My memory is composed of 2 512MB and 2 256 sticks of DDR400 Corsair platinum XMS. A total of 1,536MB of RAM.
My choice for PSU was an Aspire ATX AS500W. It's a great PSU with a transparent case and UV sensitive neon-green cable sleeving. The PSU has two, four blue LED fans,1x intake and 1x exhaust. It acts like a wind tunnel. You can also adjust the speed of the fans, there is a nob on the back. The down side of this PSU is it lacks another four pin molex cable.
Lastly, I have 5 blue LED case fans and a neon black light. One particular fan I added, or should I say cut and placed on the side panel where it can face the graphics card and blow fresh air to it. A nifty mod to help cool that 6800. I will explain later on how I did this.
Oh, almost forgot, I have a Sony SDM-HX 73s 17" TFT Monitor, it has 2 buit in speakers, but I have never used them. I have my Creative 5.1 Inspire speakers for sound.

I chose to go Nvidia because they stuck with AGP cards and didn't jump the fence like ATI and just go PCI-Express for their highend cards - they waited. Plus I like the easy to install drivers and GPU menu system, not too mention I'm a bit of a fan boy, I guess since all the rest of my cards were Nvidias,
As for the processor, I chose AMD64 after reading and watching alot of news sites. I saw Intel falling behind in gaming and technology, not to mention the heat those things give off, no thank you. I prefer my processor to be a processor and not a grill!

The system worked for a while, untill I bought an extra pair of RAM and found out the last two memory DIMMs were not functioning, so I went back to Frys and they were happy to exchange the motherboard, but just to be safe, I had the processor exchanged and I traded my first pair of sticks (2x256) for a pair of 512s. Since then no problems, not even a hiccup.

My favourite part of the system would have to be the lights, you should see this thing lit-up at night.

What sucks is the case, there's very little room, not to mention it has sharp edges in it on which I cut my self multiple times working on it. It's also very loud with 5 fans and 2 PSU fans going at full.

Here is how I modded my case, I first had to unscrew the acrylic panel. I used a 3" hole saw. I had to cut in short brief bursts, so that the hole saw would not get too hot and melt the plastic. Once the hole was made, I had to place the 92MM fan up to the hole and make my marks for where the screws would go. Then I used a special drill bit for drilling called a spur point bit. It drilled like butter. Sorry I don't remember the size, but it should be the same size of all other fans screw holes. I also used a jig saw blade by hand to cut better vent hole for another side panel fan.

I am currently thinking of getting an Aspire case. Here is the link: http://www.xoxide.com/xxalmib.html I would like this case rather than the Navigator because it has some nice features such as a sliding motherboard tray, and it doesn't have those silly looking front LED lights. I will mod this case to suit my needs. I will also get another Western Digital 120GB SATA hard drive and have it set up via RAID.