Need Help, dosen't have permission for harddisk c

If that doesn't work, or you're seeing this behavior even on files that don't reside directly on the root of the drive, right-click one of the files/folders exhibiting the problem, select Properties, go to the Security tab, and click Advanced.  Please post a screenshot of that.

If you click Continue, does it work?  By default, only the Administrators group has permission to modify files residing directly on the root of C (as opposed to residing within subfolders), and since even admins don't run with elevated privileges all of the time, the prompt you're seeing is triggered by UAC. By clicking Continue, you're allowing your account's elevated privileges to be invoked in order to modify such files.

That's very strange given that your own user account (I assume you are this user Mads?) is listed as the owner, and even the regular Users group has Full Control.  Therefore, attempts to modify or delete that folder should not even require clicking Continue on a UAC prompt.  As a workaround, you can try downloading a utility called Explorer++.  If you right-click its icon and choose to Run as Administrator, it will give you a way to browse your folders using your elevated privileges, which may allow you to delete that folder.  If not, or if this problem is more widespread and you therefore want a real solution rather than a workaround, the only other suggestion I have would be opening Command Prompt (right-click it and run it as administrator as well) and "chkdsk c: /f", since part of that involves checking for corrupted security information.

chkdsk c: /f dosen't seem to do anything, and Explorer++ gives the same message, that my acces to the folder has been denied.

i right click on Explorer++ and choosed "Run as admin". then i locate the file in Explorer++, and try to delete it, only yo get the same message.

running CHKDSK results in this

after which i press "y", and it asks me to restart. but even after that restarting, nothing happens

Can you confirm that you launched Explorer++ by choosing "Run as administrator" to use elevated privileges?  And when you say CHKDSK didn't do anything, do you mean that it didn't fix the problem or the command literally didn't do anything?

Hmm, that's not good.  If you enter "Y" there, when you next restart, you should see a message that the disk is being scanned for errors.  If you have a way to boot to the Windows Recovery environment, you can launch a Command Prompt from there and scan the disk, although in the Recovery environment it's possible that your C drive will be assigned some other letter.  But if Explorer++ even running as admin can't delete those files even though the NTFS security settings indicate that you should be able to delete them even WITHOUT admin privileges, then something definitely seems wrong with the file system.