[Ubuntu][Fedora][Linux Mint] not "detecting" disks at installation wizard
This was quite a hard problem to solve, as there aren't many online sources to solve this. But in the end I still found the solution in Linux Mint Forums. If you can access disks from partition programs like GParted but not from the installer itself, it may be that your hard disk may still have embedded raid metadata, if you remembered that you did raid before on the hard disks.
So, to remove that metadata, type in a command, in a live cd.
sudo dmraid -r -E /dev/sda
Where the disk used in this example is /dev/sda. This should make the installer detect the disk again. Alternately you can boot with the nodmraid option.