Default NTFS Permissions in Windows 7 - Microsoft Community

icacls * /T /Q /C /RESET

This seems to be as good as it gets. It will overwrite permissions of files and subfolders with those of the current directory.

If you get permission errors on anything, you need to take ownership of all files first:

takeown /f * /r
icacls * /T /Q /C /RESET

You probably also want to run cmd with administrator permissions.