I have spent a few days playing around with different boot scenarios to remove Fedora and install Ubuntu but keeping dual boot with Windows 7 intact and here is the juice of my experience 🙂
* If you are booting from USB live disk make sure to disable UEFI from BIOS options and run in legacy mode (sometimes referred as CSM)
1 – Use Disk Management from Windows (Run -> diskmgmt.msc), find the Fedora partitions, delete them and format but this will delete GRUB and you will not be able to boot hence you need to restore MBR.
2 – To restore the MBR using Ubuntu live CD you should simply install lilo
sudo apt-get install lilo
sudo lilo -M /dev/sda mbr
3 – Then you can install Ubuntu normally alongside with windows using the installer which will be able to automatically detect Windows 7 installation.
This should be the perfect scenario but actually this is not what really happened to me during my trials,
What happened to me is that I damaged the MBR by accident so I got the error
BOOTMGR is missing.
after rebooting the machine.
So I plugged in the ubuntu live usb disk -> install and when asked where to install I chose something else then I chose the 2 Fedora partitions as the installation partitions and checked the option to format them
/dev/sda1 -> /boot
/dev/sda2 -> /
Ubuntu installation automatically fixed MBR and installed GRUB and now I can happily dual boot Ubuntu 12.04 and Windows 7 🙂
So I guess this is a second and an easier method to install Ubuntu >= 12.04 over fedora just by using the live disk and choosing fedora partitions as Ubuntu installation partitions.