google is your friend here. Look for manufacturing information on each PCI/ISA card (version numbers, serial numbers).
Also do a search on the manufacturer of the system or motherboard.
example:
google.com->drivers [insert serialnumber/manufacturer here] download
if you don't know any of this info, you'll have to take apart the computer case and inspect each card and component to find out make/model info
Right, I was hoping i implied this by 'looking on each pci/isa card.'
Even if you don't know the manufacturer of the card sometimes just typing in the serial number located on it will return the needed results.