Is there a way to enlarge the root partition without having to remove programs or making a new customized install ?
If you have some unallocated space after
the root partition, you can probably enlarge it with almost any partition manager. The operation will be fast and is relatively safe.
If you have some unallocated space before
the root partition, try enlarging it with GParted. The operation may take quite a long time and is slightly more risky.
If you don't have enough free space before or
after, you have to shrink an adjacent partition first. If the adjacent partition is a logical partition, you may have to resize the extended partition holding it too. (For instance with DiskDrake this is not necessary.)
When you change the size of a partition, don't forget to back up any important data on it first. A partition manager like GParted is not likely to trash it, but you never know.