Windows 7 drive C cannot read or write files

1. When files cannot be created on drive C or files cannot be installed:
Solution:
Run cmd as the administrator and enter
Icacls C: // setintegritylevel m
Icacls is a command line tool that displays or modifies the Random Access Control List (DACL) on a specified file and applies the stored DACL to files in a specified directory. Icacls.exe replaces cacls.exe for viewing and editing DACL. Icacls is an upgraded version of the cacls tool in Windows Server 2003 sp2. It can be used to reset the Account Control List (ACL) and backup ACL in the file from the recovery console. Unlike cacls, icacls can correctly transfer the changes and creation of the inherited ACL. For more information about icacls usage and commands, Run "icacls/?" at the command prompt /?" . Here I should be improved upgrade of cacls.
2. access the file and obtain the permission to the file:

1. Right-click the folder to view its properties. Click Security> advanced> owner
2. Click Edit → other users or groups, enter your user name in the name of the selected object, and then confirm
3. Select Replace sub-container and object owner
4. Click OK. A dialog box is displayed. Click OK again! In this way, we have ownership of this folder.
Note: If you do not select "Replace sub-container and object owner", we only have the ownership of this folder and will not obtain the ownership of all files in the sub-folder and sub-folder.
5. Click "permission"> "edit"> "add". Enter your username and click "OK ".
6. Click your username> edit, and then select "full control/allow". OK
7. Then, select "replace existing inherited permissions on all future generations with the permissions that can be inherited from this object ". Click application, OK, OK, and then confirm. In this way, we have all permissions for this folder.