Last night I was having a problem with reinstalling ubuntu through wubi on a PC, I had installed it first, and booted into it after the installer was done, through an automatic reboot into ubuntu option, it worked fine, but after few minutes it just froze (lack of a better processor) so I did a hard reboot (pressed the hardware power off button) and went into ubuntu again and it gave me an error saying error: file could not be found and I booted into windows made sure everything was working, which it was, and then shut it down and booted ubuntu with the same error message, so I went into windows and uninstalled ubuntu by going to control panel, uninstall a program, and then I uninstalled ubuntu, then I ran the installer again but it says the file ubuntu in C: already exits, so I went to Windows explorer and tried to remove the ubuntu file, but it kept saying that I do not have permission to use it's contents even when I am an admin?
It's corrupted. That's why you don't have permission. When it 'froze', it was not 'frozen' - just your screen probably. The hard reboot corrupted the
So, two things. First with linux you can often safely reboot even if the screen is frozen via some special keys that the kernel responds to: https://en.wikipedia.org/wiki/Magic_SysRq_key
That would have avoided the problem in the first place.
The second thing is that it likely froze due to some hardware incompatibility. Commonly this is that your graphics driver isn't adequately supported by the open source drivers installed by default with Ubuntu. So you should boot with
Finally, to fix the problem you have now, you will need to run
This answer shows how to run