Lost admin access to my computer due to corrupt user account (win7)

Question

I cannot access my user account (the default "User") on my computer (Win7) anymore as it was somehow corrupted when my computer had frozen and I had to press the power button to do a hard restart.
So now at the login screen, when trying to login using this user, the error "The user profile service failed the logon, user profile cannot be loaded" is displayed.
A short while ago I added another user, but it has no administrative rights and when CAS prompts appear to ask for admin ("User") password, and when I enter the password it fails again because this User account is not accessible.
So basically I have no admin access to my computer and no easy way to access my files. I figured out though that I can boot my computer with a Linux live CD and at least get to my files.
The user with administrative rights is also not available from safe mode.

My question would be - how can I get an admin access to my computer?

[edit] I should probably mention that it is not that my password was changed, but that some system files internally got corrupted. After the Code Access Security prompts (when I am logged in in the other account that is available to me) nothing happens, but I can see in the event log that "file was not found" or something similar.

[update] I found a related article here which applied to my situation. In safe mode I managed to get to regedit, where I found out that there was a .bak added to my profile key under the following registry key

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList 

I removed the .bak from my account and added the bak to the other entry (as described in the linked article) (which had my SID) and now I still cannot log in into my account, but I get a different error when trying to log in. It says: "The group policy client service failed the logon, Access is denied"

Answer 1

You can of course use tools listed before this post or Ophcrack. I think it would be a good idea to also figure out why your computer froze and why it changed or corrupted your password. Forcing the power off on your computer should not change your password. This is an indication that something else is wrong. You probably either have malicious software or a dying hard drive that just happened to corrupt files critical for logging in. I think a virus is more likely. I would first check the S.M.A.R.T status of the drive (if your lucky it'll tell you if it is dying). I would then backup any critical information and then take the hard drive out and run as many different virus scanning products on it as you can from another computer. This site might help.

Answer 2

I would recommend attempting to use Kon-Boot. That hopefully would be a quick and easy way of solving the problem. Simply boot with the disk and don't worry about the password.

I have used Kon-Boot before and it has rarely failed me. Hope this helps.

Answer 3

You can modified user group and permission with Offline NT Password & Registry Editor, with this tool, you can promote a user to admin.