The short answer is "probably not." There are technologies to band two network cards together, but the switch that you connect the two network cards to must be configured to support it. Furthermore, the performance bottleneck would have to be the system's LAN connection for you to realize any performance benefit. This isn't going to be the case for just about any type of Internet connection. Generally, the LAN connections are the fastest link between two systems on the Internet. The connection that would most benefit from the performance improvement is from the ISP to your home or office.
This was first published in October 2002