Thanks for posting.
Unfortunately you may not be able to find drivers for Windows 7 in this computer as it was only supported with Windows XP. You could try to check with the video card manufacturer's website to see if one is available.
Unless the card has 128 megs of ram it may not work with windows 7. Vista drivers may be an option depending on which card it is. The other option is to use a newer card like an asus EAH6450.
Years ago I used a directx 10 radeon 4650 and vista drivers.
ATI Radeon HD 4670 HD4670 512MB DVI PCIe Video Card M639J
ATI RADEON HD4670 512MB (320-7771)
ATI RADEON HD4670 1GB Part# : 4670PE31GDTSB | Dell Part# : A2479831