If you are in a mix mode environment with XP and Win7 using roaming profiles you are going to have some issues arise like this. Windows 7 stores the profiles in different directories and also has a different naming convention for the profile folders (v2).
Because you are in a mix mode environment you are going to have to manage 2 profiles for each user (1 for XP and 1 for Win7).
What I would suggest is using the USMT (User State Migration Tool). Take a look at the following link to get more information on the USMT.
http://technet.microsoft.com/en-us/windows/dd671583.aspxHope this helps~!