Copying from one Hard Drive to an External

This should be relatively simple (or so I thought), but I am running into problems copying files by simply opening the contents of the local C:\ drive and dragging them to a Networked External Hard Drive. It seems that just about every five minutes, I am receiving errors that the process must stop for various reasons. Space isn’t the issue as the external drive has 500GB and the local C:\ drive is well under 80GB. Is there a way of doing this with functionality built into Win XP Pro?

Thanks everyone as always,
Nate