Wireless is usually about half the speed of wired even with good wireless reception. You should try to optimise your reception and avoid interference.
1) raise the router above furniture level
2) Experiment with channels (some will work better or worse depending on your environment)
3) If you can detect strong neighbouring wifi, use a channel 5 stops away from strongest.
4) Relocate cordless phone base or video sender etc.
5) Be prepared to move the computer (or at least turn it so your body is not between the router signal and the wireless adapter's antenna.
At that kind of speed i do not think you should be whining at the wireless interface check the kind of files you are transferring and then look at the read and write speeds of the hardrive. It could be that the folder has a lot of individual files that the drive has to contend with. Probably the Drives Read and Write speeds i would think.