Why do I get the error: 'Device eth0 does not seem to be present' when attempting to activate my netword card?

You may need to install the appropriate module for your card. Issue the following command:

lspci -n

Example output is:

# lspci -n
00:00.0 Class 0600: 8086:1a21 (rev 02)
00:01.0 Class 0604: 8086:1a23 (rev 02)
00:1e.0 Class 0604: 8086:2418 (rev 02)
00:1f.0 Class 0601: 8086:2410 (rev 02)
00:1f.1 Class 0101: 8086:2411 (rev 02)
00:1f.2 Class 0c03: 8086:...