Upgradng my Dell Studio 540 desktop

Hey everyone, I decided a couple weeks ago to upgrade my desktop after seeing my scores on some benchmarks. I really

want to to be able to run games like crysis and such and a decent frame rate, and with good graphics. My questions are can I

upgrade any of the parts on this pc. I know I might have to replace my power supply since its 200-240V. I'm looking to get a

new graphics card/s, and maybe get a second hdd. Dunno how much of this info you need so let me know if you need more, thanks all.

Mainboard : Dell 0M017G
Chipset : Intel G43/G45
Processor : Intel Core 2 Quad Q9400 @ 2666 MHz
Physical Memory : 4096 MB (4 x 1024 DDR2-SDRAM )
Video Card : ATI Radeon HD4670
Hard Disk : WDC (500 GB)
DVD-Rom Drive : HL-DT-ST DVDRWBD GBC-H20N ATA Device
DVD-Rom Drive : WXQVS C9EVO56VOHM SCSI CdRom Device
DVD-Rom Drive : WXQVS C9EVO56VOHM SCSI CdRom Device
Monitor Type : Dell Computer DELL S2409W - 24 inches
Monitor Type : Samsung SAMSUNG - 7 inches
Network Card : RTL8168/8111 PCIe Gigabit Ethernet Adapter
Operating System : Windows Vista (TM) Home Premium Home Edition 6.00.6001 Service Pack 1
DirectX : Version 10.00
Windows Performance Index : 5.7 on 5.9


General Information :
Manufacturer : Dell Inc. (Dell)
Product : 0M017G
Version : A00
Serial Number : ..CN74431947056F.
Support MP : Yes, 4 CPU(s)
Version MPS : 1.4

Chassis Information :
Manufacturer : Dell Inc.
Type : Desktop
Version : 01
Serial Number : GL0R4K1
Asset : Unspecified

OEM Support SLIC :
HPET : Yes
SLIC : Yes
SLP OA : v2.0

Sensor Information :
Hardware Monitoring : Asus F8000

On-Board Device Information :
Embedded Controller : Yes

Slots Information :
Slot PCI-Express : 64-bit [3.3v, Shared Slot Opening] - In Use
Slot PCI-Express : 32-bit [3.3v, Shared Slot Opening] - Empty
Slot PCI-Express : 32-bit [3.3v, Shared Slot Opening] - Empty
Slot PCI : 32-bit [3.3v, Shared Slot Opening] - Empty

External Connectors :

EEPROM Information :
Type : EEPROM Specific
Address : 0x57