Permission in NT4

Greetings,
In my office one user has set permission on c: and it subdirectories as NO ACCESS for ADMINISTRATOR. so now the problem is no user on domain with administrative previlages can login on the workstation. The local administrative login is also not working. so please tell me guys how to remove this no access for administrator on thwe workstation. Is the workstation now out of use or needs formatting.
regards,
vijay