You are getting the best your net can do. With a 100mb LAN you cannot use Jumbo Frames.
Also, compare apples to apples: You say you get 10MB transfer. That is 100mb. LANs are rated in mb (mega bits). The transfer shows MB (mega bytes). A byte is 8-bits. Add (simplifying here!) a start and stop and/or parity bit and you have 10-bits.
The other issue is what the PC shows is really not a true transfer rate; it is an average. You (I do) see some drives start at a high rate (as much as 25MB) then slowly drop. It is averaging.
USB 2.0 is, effectively, faster than a 100mb lan. And, don't forget you are bound by the transfer rate of the HDD itself (buffers, latency, read access time) and file sizes.
I hope this helps.