MDT 2012: When a Refresh deployment was made to a Windows 7 x64 computer to refresh it to Windows 7 x86, computer could not startup.

The client computer to be refreshed had a Windows 7 x64 installation , and had a 100MB system reserved volume.

Then I want to refresh the x64 to x86 with the Task Sequence of Windows 7 x86.

From within the client computer, I  manually excuted scripts\BDD_Autorun.wsffrom the deploymentshare folder on the MDT server.

In the Task Sequence of Windows 7 x86, I disabled the "format and partition disk" step.  And I set the "Install Operating System" as "Next available  formatted Partition".

After the deployment finished, the computer restarted automatically and stopped at a screen, which said thatthe Volmgr.sys has someting wrong.

Could some one tell me how to solve this problem?

Thanks a lot!