Computer Heads. HELP!

[denni5themenace]

I bought a new computer the week of Christmas. I bought the parts separate from Newegg.com and assembled it on my own. It worked for about a week then itcrashed. The computer shut down and upon restart, it kept on resetting. It would load the very first screen and then it would just start again. I triedswapping out the parts. I got a new motherboard, a new hard drive, swapped out graphics cards, only used one stick of RAM, but the problem still persists.I'm still under warranty for some of the components but Newegg.com wont accept returns unless the item comes with its original packaging. I'm missingthe original packaging for my processor, graphics card, and RAM. I was thinking of buying the parts from other stores and just returning my old parts in themsaying they were defective. Will stores be able to tell if the part is different (are there serial codes on the parts that the store can check)? Any ideas towhat the problem is?

Cliffnotes:
Built a new computer
it crashed and doesnt start but keeps resetting.
tried swapping out the parts but the problem persists
dont have original packaging so i cant return to newegg
help