Re: Multiboot 2 distros on 1 HDD
Pay attention to oldfred's comments on GPT. You claimed that your first partition is "grup bios", which I'm guessing is a distortion of GNU Parted or GParted's identification of a drive as having the "bios_grub" flag set. If so, it's almost certainly a GPT disk, which is not subject to the primary/extended/logical issues that others have described.
If you're not sure what you've got, please run the following command on your current installation:
Post the result here, between [code] and [/code] strings. That will tell us precisely what sort of partition table you've got.
sudo parted /dev/sda unit s print
If I've suggested a solution to a problem and you're not the original poster, do not try my solution! Problems can seem similar but be different, and a good solution to one problem can make another worse. Post a new thread with your problem details.