I used gpart to partition a 600g hard disk with preinstall win7. When I boot up after that, boot sector for win7 was gone or maybe replaced. The grup rescue command prompt appear. I couldn’t fix it.
I simply install Linux and got a new boot menu.
When I migrate win7 to virtual box the same problem appear. This time I had to use win7 rescues disk to fix the problem. Below are the steps I found
1. Put the Windows Vista installation disc in the disc drive, and then start the computer.
2. Press a key when you are prompted.
3. Select a language, a time, a currency, a keyboard or an input method, and then click Next.
4. Click Repair your computer.
5. Click the operating system that you want to repair, and then click Next.
6. In the System Recovery Options dialog box, click Command Prompt.
7. Type Bootrec.exe /FixMbr, and then press ENTER.