The default Windows Explorer file copy function does not have features like resuming copy, controlling speed etc. SuperCopier is a replacement for Windows Explorer's copy functionality. SuperCopier replaces Windows Explorer file copy and adds many features. These include transfer resuming, copy speed computation and control, improved copy progress display, copy list editable while copying, copy list saving/loading, and an error log.
The feature I liked most is the transfer resume functionality which is much needed in Windows Explorer.
SuperCopier is still in beta and a freeware, but not supported by Vista.