How to deduct/depreciate/take Sec. 179 deduction a computer being paid off over time?

To claim a deduction for the 2016 laptop used in business, you can amend the tax return for that year. A new laptop would qualify for a 179 deduction and/special depreciation allowance making it possible for you to recover the entire cost in that year (if you had a profit)

Or you can claim depreciation of 5 years or some combo of depreciation and the the 179/special depreciation allowance.

Those would make sense if I had fully paid for the laptop in 2016. But, as I noted, I paid for it over time, beginning with some payments in 2016 and ending with some in 2017.  So how to deal with this situation?

It doesn't matter how you paid for the laptop its cost recovery is the same-5yrs or some combo as outlined above.  The deduction begins in 2016 when the laptop was placed in service.