Need suggestions/help for computer

[[RawR]sharpstonE]

al right, here's the dilyo

i'm looking to upgrade my graphics card and processor as well as purchase more RAM. however i am fairly lousy with this kind of stuff, null buying ram. all i know is that i do not want extreme bottlenecking to occur, and don't want to waste time and money.

my computer specs:

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System Information
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   Operating System: Windows Vista™ Home Premium (6.0, Build 6002) Service Pack 2
           Language: English (Regional Setting: English)
System Manufacturer: Dell Inc.                
       System Model: Dell DXP061                  
               BIOS: Phoenix ROM BIOS PLUS Version 1.10 2.5.0 
          Processor: Intel(R) Core(TM)2 CPU          4400  @ 2.00GHz (2 CPUs), ~2.0GHz
             Memory: 2046MB RAM
    DirectX Version: DirectX 11

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Display Devices
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        Card name: Radeon X1900 Series
     Manufacturer: ATI Technologies Inc.
        Chip type: ATI Radeon Graphics Processor (0x7249)
         DAC type: Internal DAC(400MHz)
   Display Memory: 1275 MB
 Dedicated Memory: 509 MB
    Shared Memory: 766 MB
     Current Mode: 1680 x 1050 (32 bit) (60Hz)
          Monitor: Dell E228WFP
      Driver Name: atiumdag.dll,atiumdva.cap,atitmmxx.dll
   Driver Version: 8.14.0010.0647 (English)

this card blowss. i got it for free from my sister's boyfriend a couple years ago. i have to set the fan speed using ATItool to 100% whenever i game(hella loud) and even then, the temps still rise above normal and i get artifacts in some games.

what i would appreciate are suggestions for graphics cards and/or processors that would compliment my computer well or if i should just get a new computer altogether(suggestions for affordable custom building? sites etc.) seeing as my current desktop/card are prettyyy damn old.

i can post some other specs if it'll help you help me

~thanks