Apparently that's completely normal. If your wireless cards are being used for the net Windows throttles network speeds to 5mb meaning you get about 1mb left for transferring files. However... There is a way to actually get the wireless in use on the net and use the wired cards for home networks.
Now I don't know if this is because I am using 7 Pro on each machine and thus the networking allows better use, or, whether this would work in any version of 7.
The way to do it as instructed (and working after a reboot) is to go into the network and sharing center.
Click on change adapter settings.
Make sure the wired card is enabled.
Right click and select properties. (the wired card)
Under networking (left side tab) right click Internet protocol version 4 ( TCP/IPv4) and go to properties.
On the first PC use the IP address 192.168.5.1 (as apparently this won't clash with your wireless cards)
It will then say it needs a subnet mask. Click OK and it (by default) will add 255.255.255.0
Click OK a few times until it closes. Then go to the second PC, enter the properties of the other wired card (after making sure it is enabled) and follow the above only use 192.168.5.2
As you do that it will add the same subnet mask. OK OK OK etc then reboot both machines.
And hey presto !
With the wireless being used for the net