Running 2 distros along side of each other.
 

I hope this hasn't been posted elsewhere,if it has, please post the link. I have a ASUS laptop with a 250GB H/D. Only one partition which I'm running Mint 15 and want to run Saybayon next to it. When I try to install it it gives the options of:
1 Use All Space
2 Replace Existing linux distro
3 Shrink current sys
4 use free space
5 create custom layout,
but no run alongside another OS. I tryed gparted to resize but come up with one half of the H/D being unallocated. That's my issue. I'm looking for advice.
Thanks in advance.