Mother board Model - DG31PR
Chipset Vendor - Intel
Chipset Model - P35/G33/G31
Chipset Revision - 10
Southbridge Vendor - Intel
Southbridge Model - 82801GB (ICH7/R)
Southbridge Revision - A1
Graphics:
Intel(R) G33/G31 Express Chipset Family
Memory 224 MB
Memory type 2
Driver version 6.14.10.4885
Processor:Intel Pentium 4 CPU 3.00Ghz
Wondering whether it supports Geforce 8400GS 512MB PCI-E Graphics card.

Yes, but not in conjunction with the onboard graphics based on Intel Desktop Board DG31PR Technical Product Specifications (http://downloadmirror.intel.com/15064/eng/DG31PR_TechProdSpec.pdf) and Wikipedia: GeForce 8 Series (http://en.wikipedia.org/wiki/GeForce_8_Series).