Computer doesn't want to turn on.

[entrust]

Hi. I've recently built my new computer and it was working fine for one month until today.
I wake up, press power button, it turns on loads something and turns off. I think WTF and do it again, nothing happens. I try to press power button few other times and it turns on for a little while and shuts off again. Now it won't start even for a little while, but the power switch and reset switch on motherboard are alight. I made troubleshooting and took a few parts out to rule them out and I think the power switch on my case is working and I suspect that my PSU is to blame here. When I opened the box for the first time, there was sing of usage on it, like it was repaired before or something.
Today is Saturday and it might be harder to get some help in repair center, so I'm looking around and maybe I will find some solution. I thought maybe I'll go to BestBuy or some stuff like this and get PSU and try it, I can always return it anyway. :/
I don't know how Newegg works, but if they give me refund for this one, I'd get new one today in New York as I hate waiting eh.

[OhpUldum]

Usually parts purchased through Newegg have to be returned via RMA and they will send you out a replacement part. Rarely do they do a refund. You could pick up a power supply from Best Buy for the time being then return it once you get your RMA'd power supply back from Newegg. Baring in mind Best Buy will have their own set of return policies.