Which is right, unorganised or disorganised?

Answer 1

Neither and both.
Unorganised means that whatever the item is it has not been organised in the first place.
Disorganised infers something that once was organised is no longer

Consider these:
The group of men were unarmed.
The group of men were disarmed

The first is a negative statement which shows a state AS IS
The second denotes a CHANGED-ALTERED STATE which can be more negative than the original one

Similarly:
John is unassociated with that company.
John is disassociated with that company
You can now see that in certain cases the prefixes un and dis can have quite a profound change in meaning let alone emphasis.
Un is really Non-something.Dis is really denoting an altered state and to a more negative one viz disjointed,dislocated,disenchanted,disenfranchised.

Answer 2

They are both real words, but disorganized is more frequently used when referring to a person. Unorganized is used to refer to a place or thing (e.g., an unorganized filing cabinet or office) or to not belonging to a labor union (e.g., an unorganized shop).

Answer 3

If you can't find your dictionary, it's probably because your workplace is disorganized.

But if you can't afford a dictionary because your co-workers won't form a union to put pressure on the boss for higher salaries, then your workplace is unorganized.

Answer 4

They're roughly synonymous, but I use "unorganized" if I am referring to something that had never been organized. I use "disorganized" to describe something that is organized poorly.

Answer 5

Very clever you, answer is unorganized