Alright it's me again...
2 days before I have my old 160GB HDD died and I need to buy a new HDD for Windows...
As my other HDDs is full of things.
Then after I install Windows 7 And reboot, is says BOOTMGR is missing
Then I disable my 500GB HDD then it boots fine!!
(WTF)
I've checked the bootmgr file is on C:\
so any one knows what happen?