I've heard that WinXP installs bridging functionality by default with you have an Ethernet interface and a wireless/firewire interface. That might be what that driver is for. I guess it's a "feature".

As the I/O interconnect world has transitioned from PCI to PCI Express (PCIe), bridge ICs have filled a critical role: to allow designers to continue to use existing PCI and PCI-X endpoints in ...

I'm not familiar with LAG or what you mean by switch running Linux, not something I do, but from a simple search it looks like it's just a bonded port more or less. So something like ip link add name ...