My Internet Problem

Hi
We have just updated from BT to Sky broardband. On our home network we have four computers all of witch are cable connected to the router. The problem is my wifes computer will no longer connect to the internet, but the home network is OK and all the other PC's are working fine. I have run through every way Manually and Automatically to get connected but I cannot get rid of the "Unidentified network" I have finaly come to the conclution that the problem is her motherboard. Now if I am right could I add a LAN Card to her computer and it would again work or would I have to replace the motherboard.
Any advice will be appreciated.

Hi there, I don't think it is a motherboard problem I would think a bad driver or virus is more likely to be your problem.. try doing a system restore to when it was working fine.. or even better backup all your data and format the HDD then reinstall Windows and drivers if it still don't work after that let me know..