Ethernet Controller (3Com 3C920) - Installation Error

I have a Dell Dimension 8100 which has a built-in integrate NIC - 3C920
(compatible with 3C905C-TX). Windows Vista Ultimate set-up [clean install
formatting previous MS Server 2003 partition] failed to install the
appropriate drivers. I have loaded and expanded the 3x91c EtherDisc Disk1
software. Using the control panel/system/Device Manager and Update Driver for
the NIC gives the following message:
"Windows encountered a problem installing the driver software for your device
Windows found driver software for your device but encountered an error while
attempting to install it.
3Com 3C920 Integrated Fast Ethernet Controller (3C905C-TX ccompatible)
There is no driver selected for the device information set or element."

I've run out of ideas and options on how to tackle this problem - no
network, no activation, no updates - other than to buy a new card. Help me
please