Always read the contracts carefully. "No interest if paid in full within 12 months" Interest will be charged to your account from the transaction posting date if the purchase balance is not paid in full within the deferred interest period. Limited-time offer for qualified customers   DFS link 
Bought a Desktop a year ago on a promotion that advertised 0 interest if paid within 12 months. So you go ahead and let me know how you read that. The way that I understand it is that if you don't pay off the computer within 12 months they'll start charging you interest. WELL NO, if you don't pay it off within 12 months they're going to backdate 12 months of interest at 21%. And there's nothing you can do about it. I just paid $3,000.00 for a computer I've only used a couple times because its slow as molasses and overheats. 
No interest if paid in full within 12 months not true