If you like and applied the trick that changes the default user profile location to different partition, then too bad, Windows doesn’t like this approach and gives you this warning message that basically stops the upgrade process. You won’t be able to upgrade your system to the latest awesome Windows 7 because of that, unless:
log off your current user and log into a different user to prevent your profile from being messed up during the installation.
Fired up regedit.exe, and make the following changes.
1. Reverse ProfileDirectory registry key from HKEY/Microsoft/Winodws NT/CurrentVersion/ProfileList back to default, or at least point to the C: or whatever the system drive locates.
2. Temporarily change ProfileImagePath from the each profile sub key under ProfileList to the different location to the C: or whatever the system drive locates.
Start the upgrade process again, and this time the compatibility check will pass and you are on the way.
Once the upgrade process is done, before you log in to your user account, change the ProfileDirectory registry key from HKEY/Microsoft/Winodws NT/CurrentVersion/ProfileList to where your original user profile stored.