User State Migration Tool 4.0 Hard-Link Migration
The User State Migration Tool (USMT) 4.0 is part of the Windows Automated Installation Kit (Windows AIK) for Windows 7. USMT offers command line tools for migrating user files and settings from one computer or operating system to another and for controlling which files are migrated.
You can download the Windows Automated Installation Kit from the Microsoft Download Center.
USMT 4.0 hard-link migration is a new feature that you can use to perform an in-place migration much faster than by using traditional file copy mechanisms. Hard-link migration in USMT scans the computer for user files and settings and then creates a directory of hard links to those files. The hard links are remapped into the appropriate locations in the new operating system. The entire process typically takes a few minutes to run, does not duplicate files on the local disk, and can save several hours when upgrading to Windows 7. You can use USMT hard-link migration both online and offline. This document explains how to use USMT to migrate files offline from a default clean install by using Windows.old. For more information about online scenarios, see the User State Migration Tool 4.0 User's Guide.