This is specifically for the Intel PRO/100 VE
My first couple of tries on getting this to work failed miserably, I then tried some other ways on my own and got it to work. Here's how I did it.
1) Goto this forum and follow his instructions up until the part about removing the kextcache
2) Instead of folling his directions open terminal and type:
sudo chown -R root:wheel /System/Library/Extensions
kextcache -k /System/Library/Extensions
3) Once this is done and there are no errors go to Disk Utility and repair disk persmissions
4) Reboot and look in System Preferences-->Network-->the Show dropdown to see if the internal ethernet is recognised
Tips and tricks
1) If you are having trouble with the airport utility opening with the card do this:
1)Open the same file used in changing the Utitily to en1
2)In that file right below that there is a string that contains <integer>0</integer>, change that to <integer>1</integer>
2) If you are getting hung at a blue screen on startup do this:
1) Search for the One Wire Trick or the paper clip trick and use that
3) If your wireless will not auto connect to a network do this:
1) Go into the Network Preference Pane and go to airport in the Show list
2) Once there change the option to Preferred Networks
3) Delete all networks out of that
4) Re add the networks you want
5) Switch it back to automatic
These are all the things I can think of right now I will update later if anything new comes into my knowledge.
Also if you have any trouble with my guide aske here and I will try to help.