I just bought the LaCie external disk drive
spec: USB2.0, 320GB HDD, 7200RPM, Seagate
When I run the HD_speed software to see the transfer rate in read and write, the max rate in both case is at best 1.3-1.5MB/sec with an average of 1meg/sec. Even by setting different block size the transfer never exceed the 1.3-1.3MB/s.
Are you sure your USB ports o hub are 2.0 high speed? Several hubs are USB 2.0, but not high speed (USB 2.0 doesn't mean 480Mbps, it's only protocol and electrical standard).
Make also sure you have the latest drivers installed for your mobo USB controller.
Some Lacie external drives also have firewire 400 and firewire 800. I've done speed tests with my Lacie Little Big disk and the only difference being the interface that I connected, the 800 was by FAR the fastest, then the 400, then USB 2.0.