I have faced problems copying large files (several hundreds megs) over a Windows Network between two Windows 7 boxes. During the copy, the process just freeze forever, and when trying to cancel it, it just tries forever without success.
At first I tough it was a antivirus/firewall issue, but disabling the software on both machines didn’t fix the problem. What really helped was this fix, that disables a feature called Auto-Tuning. It only takes one command on the Command Prompt (Start/Run: cmd) to bring it down:
netsh int tcp set global autotuninglevel=disabled
Then, restart the machine and voila, the problem should be gone.
If this does not fix your problem and want to re-enable this feature, just run:
netsh int tcp set global autotuninglevel=normal