Shrink your current partition space by 18-20GB; if that leaves enough for your long time mint installation
--it only becomes awkward if the space is not at the beginning or end of the whole drive area: if it is at the end of your current partition, then it (the space you need to use) is a simple process.
http://www.techmadeeasy.co.uk/2011/04/2 ... h-gparted/
- Format the now empty space available (space left after the shrink the partition (gparted move or resize)..
- use the now formatted space as needed..