Computer Administrator Problems + Games!

Ok.. were to beging. About 2 months ago I had to reformat . Well, I did so and while midway in the reformat, it froze so I had to "power shut"(?) my computer off (push the little button). After doing so I tried reformating again, and again.. having to do the SAME thing over and over again, shutting my computer off with the button midway through the reformat because it would freeze. To be exact, it was at the Windows XP set up screen, asking me what I wanted my computer name to be. Well, I called e-machines (my computer manufactor) and they helped me get through this, but they did it weird, it was almost like it wasn't meant to be the way they did it. They were telling me to go through all these windows and type in serial numbers (the guy that did it for me sounded arabian and said I could do it free of cost because he hated his job... ). So we did that, my computer is "prefectly" fine at the moment. Except it's not. Problem starts here!!: When ever I try to install games, it'll let me.. but it won't let me play them simply because I'm not the computer administrator. The funny thing is, I AM the computer administrator; MY account is that ONLY account on this computer. And occasionally my computer will drop back 3 hours like once a week, haveing to reset it.. I don't know of any other problems yet. And this blows because my computer stopped working after getting my new 6800!!! Please help guys, and thanks for the time!