I have 2 systems both win7. They are on the same netgear fs105 switch. The network cards are set to autonegotiate.
Now I rip my bluray movies and move them from one system to another by just copy and paste. Sometime these folder can be about 20 - 30gb. I usually see when coping I would get upwards of about 100mb/second. But sometimes I would get 20-30mb/sec. By watching the details in the copy I would see it copying a very large file and doing 30mb/sec, so I know it's not happening because it's copying multiple small files.
anyway to figure out why I'll get 100mg/sec or more at time and other times it's very slow. I have other devices on the same switch, but I check and they are in use when it slows down.