I am working on a Dell Optiplex 740 with on board ethernet card and I had to re-install the os(XP) using the CD with the desktop.  After completing the OS install hardware manager does not recognize an ethernet port on the system.   I tried to install drivers from dell but no luck.  I can't run dell diagnostics online because I can't get on the internet.   Any diagnostics I can load to test this out or is there something I did wrong?