ocal area connection doesn't have a valid ip configuration

Hi,
I have a hp desktop with windows 7 that was getting internet from an old ibook g4. Basically there was an ethernet cable connecting them that gave the ibook's internet to the hp, because the hp doesn't have a wireless card. It was working for a couple months but now the hp is not getting internet and when I try to diagnose the connection or whatever it says "Local area connection doesn't have a valid ip configuration". I don't think its a problem with the ibook because the ibook is still getting internet.
I don't know why this happened but when I looked on the system restore menu it said before it stopped working there was two critical updates. Also around that time the computer was shut down wrong or something and I had to run startup repair or maybe system restore (I don't remember which one). The only things I've tried to fix it were doing a ipconfig / flushdns and then doing a system restore to before both of the updates. None of those things worked, though.
If anyone knows how to fix it or if I should post more information please let me know. Thanks.