**My system configuration is..**
Time of this report: 7/30/2012, 22:49:26
       Machine name: XinfinitY-XINF
   Operating System: Windows 7 Ultimate 32-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_rtm.101119-1850)
           Language: English (Regional Setting: English)
System Manufacturer: Dell Inc.
       System Model: Inspiron 620s
               BIOS: BIOS Date: 04/12/11 16:24:18 Ver: 04.06.04
          Processor: Intel(R) Core(TM) i3-2100 CPU @ 3.10GHz (4 CPUs), ~3.1GHz
             Memory: 3072MB RAM
Available OS Memory: 2978MB RAM
          Page File: 1926MB used, 4028MB available
        Windows Dir: C:\Windows
    DirectX Version: DirectX3D 11
DX Setup Parameters: Not found
   User DPI Setting: Using System DPI
 System DPI Setting: 96 DPI (100 percent)
    DWM DPI Scaling: Disabled
     DxDiag Version: 6.01.7601.17514 32bit Unicode

Inspiron 620

I think the full answer would need more info like what you plan on doing /using the new video card for .
,but having a quick look with google ] your model shows it could have a 300W power supply ,not very big ,most new cards will need at best 500W or more .