|Power flickers are impossible to predict what will happen on your computer. The most serious scenario is your motherboard is damaged but it could be as simple as replacing the power supply. |
I would take the power supply out of the desktop if I were you and try just another one - you could also do the same with the power cord. If you don't have one and are out of warranty, you'll have to purchase 1 and that's not a big deal, it's less than $100 to buy usually - and of course a power cord will be even less than that.
If not, then call Dell Tech support and see what they'll get you. If they can send you another power supply that'll be the optimal next step....otherwise you'll have to decide whether you want to pay for that or a new motherboard. If you have to buy parts I'd start with the power supply, see where it goes.
If you have to buy a new motherboard and can't replace it yourself (most people can't), it's probably better to just replace the desktop, unless it's something that's essential to running a business or something.