I built a new computer with Oblivion, Crysis, COD4, and RBS: Vegas 2 in mind.
CASE: Raidmax Sagitta II Mid-Tower 420W Gaming Case w/ Side-Panel Window (Black Color)
CS_FAN: Extra 3-Color Neon Light LED Case Fan [+5] (2 x Fans [+5])
CPU: AMD Athlon(TM)64 X2 6400+ Black Edition Dual-Core CPU w/
HyperTransport Technology [+36]
CD: (Special Price) 20X DVD+/-R/+/-RW + CD-R/RW DRIVE DUAL LAYER
CD2: 16X DVD ROM (BLACK COLOR)
FLASHMEDIA: INTERNAL 12in1 Flash Media Reader/Writer (BLACK COLOR)
FAN: CoolerMaster Liquid CPU Cooling System (Superior Cooling
Performance + Extreme Silent at 20dBA) [+54]
HDD: Single Hard Drive (250GB SATA-II 3.0Gb/s 8MB Cache 7200RPM HDD
[-14])
KEYBOARD: Logitech Deluxe 104 PS/2 Keyboard (Black Color)
MOUSE: Logitech Optical Wheel Mouse (BLACK COLOR)
MOTHERBOARD: MSI K9A2 CF-F AMD 790X CrossFire Chipset DDR2/1066 Dual
16X PCIE SATA RAID MB w/GbLAN,USB2.0,&7.1Audio
MEMORY: (Req.DDR2 MainBoard)3GB (3x1GB) PC6400 DDR2/800 Memory [+100]
(Corsair Value Select or Major Brand)
NETWORK: ONBOARD 10/100 NETWORK CARD
OS: Microsoft(R) Windows Vista(TM) Home Premium w/ Service Pack 1
(32-bit Edition)
POWERSUPPLY: 600 Watts Power Supplies (CoolerMaster Unit 600 Watts
eXtreme Power - SLI Supports)
SOUND: Creative Labs SB Audigy SE [+30]
USB: Built-in USB 2.0 Ports
VIDEO: ATI Radeon HD 3870 X2 PCI-E x16 1GB Video Card - GDDR3
WNC: PCI Wireless 802.11g 54Mbps Network Interface Card
Should run everything just fine. I plan to OC the CPU a little.