Moving user profile from one computer to another on same operation system is never easy, migrating from one OS to another is even harder because the file structure may be diff in different OS. It’s always been a challenger to either end user or IT pros.
Here is a step by step Silverlight video up on Technet that shows in detail how to use the User State Migration Tool (USMT) to migrate user files and settings (aka user profiles) from Windows XP to Windows 7 using a default installation. You can also download the video in WMV format as well if you don’t like install Silverlight on your computer.
Migrating from Windows XP to Windows 7 [Microsoft Technet]