I know your pain, i also bought an external drive for keeping large video files on, usb 2 is slooooooowwww. At best I usually got only 24Mbs transfer on usb2.
I took it back and got a PCI-e usb3.0 card and a usb3 ext drive dock. Transfer was as fast as my internal drive, Biiig difference. Sell or return your usb2 ext drive and get a usb3, its worth the price difference, which isnt much. transfer now takes minutes instead of hours.. ESATA is as fast as USB3, if you prefer that option..
Also, make sure that your external drive is on its own usb 2.0 port and not on a HUB...
When you plug in your external drive, does your computer say "this device can perform faster if you connect it to a usb2 port" ?
Run run run and exchange that usb2 for a usb3!!