The first 3 octets of a MAC address provide the manufacturer of the NIC. For example, consider the MAC address given below:
00-22-75-xx-xx-xx
00-22-75 will uniquely identify the manufacturer of the NIC, which in this case turns out to be Belkin International Inc.
However, please note that identifying the manufacturer is only half a job, and you may need to try different drivers from that manufacturer to troubleshoot the problem
The following site can be used for vendor look up given MAC address:
http://www.coffer.com/mac_find/