You will not see it under Device Manager, as it is a network device, similar to how you won't see your router in the Device Manager. You didn't need to install any drivers as Windows7 has SMB (the software needed to use a network drive) installed by default.
Your transfer speeds are really good. Never worry about peak transfer speed, as the speed various on a lot of factors (size of the file, other network traffic, other programs running on your computer, etc...), and hard drives rarely operate at peak speed. Even an internal hard drive usually peaks around 25-30MB/sec, despite having a theoretically peak that is much higher.