PC will not Start Up

Suddenly my PC will not startup. I get the screen saying "Windows Starting" but that's it..... When I shut down the PC (start button) it comes back to the repair/start normally screen but I am unable to use the down arrow to start normally.

So....I have to wait about thirty minutes for MS to try and repair the problem, which it cannot. I then do a system restore which takes another ten minutes and I am told that system restore did not complete successfully, and the error Ox800700b7.

The process closes, windows starts again and opens ever so slowly. I am then told that system restore DID complete successfully? I can then use the PC normally.

Last night I shut it down, gave it ten minutes and it started up fine. I thought okay it was just a one time glitch, but this morning the same routine all over again. Repair attempt, system restore (at least an hour total), and I am using it again. What could cause this, and how do I fix it? My PC has all the HD space all the memory I need and is relatively new.

How do I run a diagnostic on my HD?

And with the scannow I get the message I must be the administrator. I am the only administrator and user?

Okay, I have no idea how to do either of these things. I tried the scannow and it says I must be the administrator and run this in the console. Can someone please tell me what this means. Again I AM THE ADMINISTRATOR AND THE ONLY USER.

Let me try this again....I am the admin but when I go to the command prompt it say I must be the admin....so apparently it is not recognizing me as the admin.

Built-in Administrator Account - Enable or Disable

Okay, I finally figured out how to run scannow as admin. I ran it and it said that it found corrupt files but unable to fix them as in see C:\Windows\Logs\CBS.log. Now what do I do?