Windows 7: Specify user which is used for checking NTFS permissions within share

There are 2 users in my OS: adm (renamed default administrator account, member of administrators) and usr (created when installing, member of users).
Folder C:\Share has been shared. For checking NTFS permissions of subfolders and files user adm is used. Therefore users of another computer have administrative rights for this folder. In computer management console, there is share session with user adm when i am connected from another computer. If i do not want give adm rights to users of another computer, how can i specify another user (e.g. usr) which will be used for checking NTFS permissions?
I cannot use share permissions because some subfolders allowed to write, some subfolders are not.
I want only one share (e.g. whole disc C:\) and use this as network drive.
And i want to have ability to map this share folder using different credentials (sometimes usr, sometimes adm) but i cannot connect as usr. Maybe i have to allow remote login some where? I do not know where.