Looking to Upgrade my PC

Hello all,
I am looking to upgrade my PC for the purpose of performance while gaming. I like to just do Free games online most are MMORPG's like Faxion.

My Current Spec's:
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System Information
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Operating System: Windows Vista™ Home Premium (6.0, Build 6002) Service Pack 2 (6002.vistasp2_gdr.101014-0432)
Language: English (Regional Setting: English)
System Manufacturer: MSI
System Model: MS-7309
BIOS: Default System BIOS
Processor: AMD Athlon(tm) II X2 250 Processor (2 CPUs), ~3.0GHz
Memory: 4094MB RAM
Page File: 2068MB used, 6336MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
DxDiag Version: 7.00.6002.18107 32bit Unicode

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Display Devices
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Card name: NVIDIA GeForce 9500 GT
Manufacturer: NVIDIA
Chip type: GeForce 9500 GT
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_0640&SUBSYS_400A1682&REV_A1
Display Memory: 2797 MB
Dedicated Memory: 1005 MB
Shared Memory: 1791 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
Monitor: LG W2361(Analog)

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Disk & ***/**-ROM Drives
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Drive: C:
Free Space: 231.4 GB
Total Space: 476.9 GB
File System: NTFS
Model: Hitachi HDP725050GLA SCSI Disk Device
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I tend to get only 20 FPS on most games near medium settings. I am looking for a simple upgrade or something I have over looked. Please advise if you see anything odd or would like to suggest an upgrade.

Thanks All!