Where to start troubleshooting Intel PRO/1000 performance problems?

[Sally Janghos]

I'm looking for some suggestions on where to start troubleshooting performance issues on a Intel PRO 1000 card.

It's installed in a box with the following configuration:
        FreeBSD 6.1
        AMD Athlon(tm) XP 2100+ (1741.42-MHz 686-class CPU)
        Dell CERC SATA RAID 2

The file transfer(ftp/smb/scp) speeds from/to this machine do not appear to go above 10Mb.  The other machine
doing the transfers has similar specs(same Ethernet Card) but is a Windows XP box.  I've tried replacing the switch with
a crossover cable between the machines and the same speed persists.  Any suggestions on where to start and what tools
should I use to do the benchmarks?

Thanks,
  Sally