Computers are listed equipment, which means there are extra rules for depreciation.
First, you must keep records of your computer use (W-2 work, self-employment, personal). If you don't have records of some kind and are audited, the IRS does not have to allow any deduction that you can't prove.
Then you can deduct or depreciate the percentage used for your W-2 job as an unreimbursed business expense itemized deduction subject to the 2% rule; you can deduct the percentage of use for your self-employment as a schedule C expense, and you can't deduct the percentage used for personal use. If no one use is more than 50% of the total, then you have to use depreciation, rather than the section 179 depreciation allowance.
You can't deduct 100% of the cost as a schedule C expense unless 100% of the use is for that work.