Windows Vista sometimes freaks out when you try to copy large files over networked drives. If you've been having problems like this, it can usually be fixed by turning off the auto-tuning that Vista does. To turn it off do the following.

1: You need to open a command prompt with administrator privileges. If you don't know how to do this, type cmd in the Start menu. But instead of hitting Enter to run the command, hold down Shift + Control while hitting Enter.

2: On the command prompt enter this: netsh int tcp set global autotuninglevel=disabled and then hit Enter.

Once you make this change, you'll need to reboot for the changes to take effect. After rebooting, you should be able to copy large files over a networked drive without any issues.