Now the enviorment:

Windows already installed and Truecrypt encrypt the whole disk. and install Ubuntu and keep Windows.

After Ubuntu installed, the Windows disappear.

Reason/Solution: Windows is encrypted with Truecrypt, so Ubuntu can’t detect the system and generate the dual-boot menu.

so we need to use “Truecrypt Rescue CD”, insert it into the computer and restart it. Then it will show: “…Install hiding operating system”

choose “No”, then it will ask your password, input your password and then go to Windows now. default it will boot into Ubuntu.

after boot into Windows. “permanently decrypt” ….then grub-install /dev/sda

we got dual-boot menu. if any better idea to keep Truecrypt with Windows. share your idea. Thanks.