Windows 7: I can't boot my windows 7 system. Because I format C.

Hello Chen:

If Windows 7 Startup Repair will not write the MBR to Windows 7 when run three separate times with reboots, then you need to mark it Active first.

Boot into DVD Repair console, click through to Recovery Tools list, open a Command Line, type:

DISKPART
LIST DISK
SELECT DISK # (replace # with Windows 7 HD)
LIST PARTITION
SELECT PARTITION # (for Windows 7 partition)
ACTIVE
EXIT

Now return to Recovery Tools list to run Startup Repair up to 3 separate times with reboots, as it will try to repair and then write the MBR to Windows 7 which was previously on Vista partition.