Clear Install Windows under Dual Boot System

I haven’t been using Windows for too long that I really couldn’t retreive the admin password back to the brain. Since I have a dual boot system (Lubuntu & Win7 Ultimate), I thought I had to wipe everything and redo the whole setup again, but fortunately Linux system can actually be preserved. We only need to redo the Windows setup and reset Linux grub.

Reinstall Windows

  1. Insert Windows Installtion disk
  2. Format the partition that is labelled Primary
  3. Install Windows on the Primary partition

After clean installing Windows, grub is gone from the startup and jump straight into Win7 system. To restore the option for choosing OS, we need to get the grub back.

Recover grub (Lubuntu 14.04)

  1. Insert Linux disk / usb and select the option “Try without installing Lubuntu”
  2. Alt + Shift + T to open terminal
  3. Run sudo fdisk -l to display a list of partitions on the hard drive
  4. Run sudo mount /dev/sdaX /mnt where X is the number labeled with Linux
  5. Run sudo grub-install --root-directory=/mnt /dev/sda to install grub
  6. Run sudo update-grub
  7. Reboot

*Note: if you get an error that say “Can’t find /dev/sdaX in /etc/fstab or /etc/mtab” from Step 4, you should double check to make sure that there are no whitespaces missing from the command.