Why waste that time and headache when checking the hardware first is
so simple? You can always skip the parts you know are good. Eventually
this stuff will become second nature to you and it won't add much time
to your machine set-ups at all.
See if it boots?
Plug it in, connect a monitor and keyboard, and turn it on. If it gets
to a login prompt, you're golden. Check the NIC if you care to and get
on with things!
Troubleshooting
If it doesn't boot, the main thing to remember is: only test one fix
at a time. Everyone breaks this rule in the interests of speed, but
just remember that eventually you're going to have to go back and check
all that stuff you swapped out, unless you want a pile of unknown computer
parts next to your desk for all eternity.
Check your peripherals.
Plug/Keyboard/Monitor cable
(boot detect issue)
Check your OS.
Knoppix
Check the machine internals.
Swap known good/reseat
Login Troubleshooting
Try console login.
Reset password.
Advanced troubleshooting.
Network Troubleshooting
Verify it's not a systemwide problem.
Check the cable and status lights.
Verify the IP address.
Other OS possibilities.
(name resolution, traceroute, ping).
Check the NIC.
Advanced troubleshooting.
(blocked at router?)