I gotta say I really like that price... this is what someone else came up with for me. Let me know what you think.
"CPU - Intel Pentium Dual-Core E2200 Retail $84.99
Newegg.com - Intel Pentium E2200 Allendale 2.2GHz 1MB L2 Cache LGA 775 65W Dual-Core Processor - Retail
Motherboard - Gigabyte Intel G31 Retail $66.99 (I consider this one a little bit better than the ASUS that you listed, plus it supports just about all of the current LGA 775 CPUs out there.)
Newegg.com - GIGABYTE GA-G31M-S2L LGA 775 Intel G31 Micro ATX Intel Motherboard - Retail
RAM - G.Skill 2GB DDR2-800 $44.99
Newegg.com - G.SKILL 2GB 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Desktop Memory - Retail
Video Card - It's hard to pick this out because it mainly depends on your preferences. Are you wanting higher settings or would you settle for middle quality settings? A very good ATI HD3850 can be had for around ~$170 or a lower end nVidia 8600GT (I would right to get the best card that you can afford. Just look at the charts that I listed earlier.
Hard Drive - Using your old one correct? $0
Optical Drive - Lite-On DVD Burner SATA $22.99
Newegg.com - LITE-ON Black 16X DVD-ROM 52X CD-R 32X CD-RW 52X CD-ROM SATA Combo - OEM
Case - The one that you picked out. $29.99/plus a case fan
If you can possibly use the one you have now, just make sure that the motherboard would fit. It would save you $29.99+the fan+shipping=~$50
PSU - I'm not hundred percent what to recommend here. A good PSU would probably be around ~$50<, but remember not to skimp on this component.
Something to go by would be a ePower 500w $46.99
Newegg.com - ePOWER ZU-500W ATX12V Ver. 2.0 500W Power Supply 115/230 V UL, CE, FCC, TUV - Retail
(This would the lowest I would go.)
Look at the 12v Rails: If it's a single look for at least 28 amps or if it's dual look for at least 18+ amps
Total ~$Under 500 dollars"
I'm comparing the two.