Windows XP Pro Gigabyte Network Card

I setup a new Win XP PC on a Win 2000 domain. The PC has a gigabyte network card. Two days later I get a message a domain can not be contacted, using a cached account. I tried rejoining the domain and two days later the same error occured. I went into the network card properties and changed the link speed from auto sense to 100 mbs trying both full and half duplex. The error message concerning the domain persists. What steps should I take to correct this situation?