|Well, for starters, you could deny access to the drive to the Administrators group and grant it only to the Domain Administrator. Then you remove the "Take ownership of files and other objects" right from the Administrators group. And you would make the Domain Administrator the owner of the drive.|
But that's an unlikely scenario. More likely, if you want people to have limited administrator privileges, you grant them just those priviliges - for example the ability to create users in an OU, but don't make them members of the Administrators group. There are a whole number of levels of "Administrator" in a Windows domain.
Most likely is that you have misunderstood what the OU wants to do. I suspect he means "restrict access to C: to those users" not "restrict those users' access to C:".