If you have a multiport switch or hub, try moving the patch cables to a different port as well. I’ve seen that, too, in addition to bad cables.
One example: Had a client complaining about slow data transfer rates (long story, short on details, not relevant).
Short story: Their IT had installed a single patch cable from the VOIP system for their phones and the hardware adjusted their speeds to 10mbps. Apparently the VOIP cables are crap for anything but phones and have the tiniest print rather than some obvious label identifying them as such.
I should’ve billed the hell out of ‘em. PITA to figure that one out. Keep an open mind or, to keep your sanity, go peer to peer with a long cable and just do the transfer (iirc your prior comment). They also make handy cable kits to connect a hard drive to your other computer. Cable kit is only $30 or so and is universal (IDE or SATA).
But if you need the bandwidth you’ll have to solve the problem.
I have a newer I7 machine with 24 gigs of memory that is reasonably fast on it's own, but the motherboard Ethernet still runs at 10mbs. I will be upgrading a Pci-E slot with a USB 3.0 soon that would have given me another route to go this time, but still, I dream of transferring a 2 gig movie from the bedroom to the living room in a couple of minutes instead of 10 minutes and leave the USB drives in the drawer. I've even thought about building a NAS but why do that if files run at 10MBS or slower?