Western Digital ATA133 80 GB HDD: Fry's $50
1 GB OCZ DDR400 RAM [2X512]: Fry's $100
Sony 16x DVDRW Dual Drive: Walmart $70
Samsung DVDROM 16X OEM: Micro-Center $20
Diamond/Stealth ATI Radeon 9550 256MB DDR: Micro-Center $65 [easy to overclock]
Turtle Beach Catalina 7.1 Soundcard: Fry's $35
MGE M1 Gamer Case with 450W Power Supply: Micro-Center $50
2X CoolerMaster Case Fans: Micro-Center $10
Antec Slot Fan/Blower: Micro-Center $5
Windows XP Home Upgrade: Wal-Mart $89 [All you need is an old Windows 9x/ME/NT or system restore disc to use as full]
After tax, a tiny bit under $600, not cheaping out on anything [this system has a good burner, a real sound card good for gaming and HT, twice the amount of RAM dual channel at that, and happens to have a case and proper cooling, 0h, and a legal operating system] If you bought all these parts online or ebay, I'm sure you could do even less than what I did.
And Tom didn't even count in shipping or tax..loser. Someone could counter his system "performs better", but I seriously think the difference in performance would be very marginal, with twice the system and video ram, less intergrated parts, and better though cheap cooling.