Fast Internet, Slow Network

Hi all,
Im in the process of building a test Win7 box, dumping as much software on it as possible to check compatibility...
I had a iTunes x64 installer on a network share, which failed "Is not a valid win32 app."
So I redownloaded it, 93.8MB in 15seconds. Thats roughly 4MB/s. Decent speed.
It installed fine.

Next piece of software is a standalone, so doenst have an installer. So copy/pasting files from the network to C:\temp, Im getting speeds of 768KB/s.
Thought that was a bit slow. I figured it might be the server.
I setup a share on my box right next to my other box, and tried copying a 6gb .iso, also getting speeds of <1MB/s
Accessing share by IP and DNS name both the same result.
Both boxes have gigabit nic's running through a gigabit netgear switch running to a gigabit port in the wall.

So the golden question is, how/why is the network speed from PC to PC, Server to PC much slower than Internet to PC.

It could be the storage medium. Copying from a PC to your PC could be slowed by various reasons
It could be that the other PC is busy with other stuff (other users, processes) and can't serve your file fast enough (low read speed is not an option for <1MB/s even with a lot of fragmentation)
If you transfer a big ZIP file your antivirus may scan it before releasing it to the application that downloaded it.
It also depends on the transfer method (FTP, SMB, SFTP, CIFS,...)