His recommendations were the following (this was from some time back, so the prices are cheaper now btw)
^-- I'm talking about UsAndThem (the guy that made the guide I linked to)
AMD Based Computer $1057.00 
AMD Athlon 64 3000+ Venice Processor $147.00
CHAINTECH VNF4/Ultra Socket 939 NVIDIA nForce4 Ultra Motherboard $92.00
Thermaltake SOPRANO VB1000SWS Silver ATX Mid Tower Case $79.00
OCZ PowerStream OCZ420ADJ ATX 420W Power Supply $89.00
Corsair Value Select (Dual Pack) 184 Pin 512MBx2 DDR PC-3200 $91.00
Windows XP Home $88.00
SAMSUNG 160GB 7200RPM SATA Hard Drive $94.00
Samsung 160GB 7200RPM Hard Drive $88.00
POWERCOLOR Radeon X800XL 256MB PCI-Express Video Card $289.00
My recommendations? (Tweaked to your budget)
AMD Athlon 64 3000+ Venice Processor $147.00
EPOX 9NPA+Ultra $109
Thermaltake SOPRANO VB1000SWS Silver ATX Mid Tower Case $79.00
OCZ PowerStream OCZ420ADJ ATX 420W Power Supply $89.00
Corsair Value Select (Dual Pack) 184 Pin 512MBx2 DDR PC-3200 $91.00
Windows XP Home $88.00
Samsung Spinpoint 200GB: $92
POWERCOLOR Radeon X800XL 256MB PCI-Express Video Card $289.00
BenQ DVD Burner $45
Thermalright XP90 Heatsink + Panaflo L1A Fan $50 (This will cool your processor better, and allow you to overclock (or make your processor run faster)).
Leaves you at $1079. Gives you about $300 for some upgrades.
-Get yourself 1 more GB of RAM (+$100)
-Get yourself an Audigy 2-ZS (+$70)
-Get yourself a Logitech Z5300e ($130) http://www.newegg.com/Product/Product.asp?Item=N82E16836121121 <-- HOT!
There's your $1300 system 
Bold represents changes made.
 
First thing you want to do is review EVERY SINGLE PART. 
CPU is an easy choice: AMD Athlon64 3000+. If you want a faster CPU, overclock it 

.
Motherboard: Just do some research (see guide in sig). The board I recommended for you  should be very easy to set up for a first timer, while STILL giving you the chance to overclock (2nd best overclocker)
Case: Haha. Decide based on Looks, Cooling (hot performance systems need good cooling), and Noise (some cases are loud).
Power Supply: Make sure you get a quality power supply. I think UsAndThem's guides explain that pretty well. The OCZ Powerstream 420 suggested is excellent though.
Graphics card: Look at some benchmarks. Find the bset one for you. Best bang for the buck now is the X800XL though.
Good luck, and most importantly: have fun!
-The Pentium Guy