Both can be used to introduce a new subject of discussion; however, my feeling is that there is a subtle difference in acceptable contexts - "with regard to" is less appropriate when the subject has not already been directly questioned. For example,
When it comes to technology, I have no idea what I'm doing
would be fine, in the context of discussing, say, a new phone but the corresponding
With regard to technology [...]
would be inappropriate unless the question of the speaker's technological ability had already been raised but not yet addressed.
Both would be appropriate, in a context of say a board meeting, where "Technology" was an item on the agenda.
You have put the words the wrong way around in your first example:
It has something to do with the car
This means it involves the car in some way. For example
My back pain has something to do with how I sit.
This means that the pain in my back is somehow related to how I sit.
Has something to do with is an idiom that means is related to or involves. The word something must come before the verb to do for it to mean this.
The other way around means, as you say, that it (whatever it is) must do something with the car. For example:
I need to do something with all the junk in my flat.
This means that the junk in my flat needs something doing to it by me.
As an aside, two related idioms are
- Has nothing to do with, which means is unrelated to or does not involve
e.g. "Having hair on my chest has nothing to do with eating the crust of my sandwiches".
- Has everything to do with, which is an emphatic form of has something to do with, sometimes used literally to mean only related to or only involves.
In fact there are many possible phrases of the form has X to do with ... . X can be, I think, any adverb that implies quantity. E.g.
- It has little to do with the car
- It has most to do with the car
- It has all to do with the car
The adverb used changes how related it is to, e.g. the car.
Best Answer
AS CED says, be/have something to do with something is ill-defined:
(ie is related to finance. Here, 'finance has something to do with what he does' doesn't sound idiomatic. Probably because 'finance' is the wider field, 'what he does' a small part or small overlapping area. But with 'equivalents', like 'locks have something to do with keys', the A and B are reversible.)
..........
(ie It might be something that results from how it's made.)
In this case, 'The way it's made might have something to do with it being so brittle' (the reverse causative; CED does not give the 'or be caused by something' sense) seems to work.