Well migrating from XP to windows 7 it is a huge pain to work with files sometimes,because the permission of the files changed automatically and and need to be changed to be used properly,taking the ownership of the file also help,but I didn't know how to change the permission of all the files at once as whenever you select multiple files and right click on them the security bar do not appear unlike XP,here is the 2 command that can do the job for you(for me the last one worked like a magic).
Use takeown from the command prompt to take ownership a folder and all subfolders & files recursively:
takeown /f "c:\folder\subfolder" /r
You can use CACLS from the command prompt:
cacls "C:\path\to\folder" /E /T /C /G "Administrator":F
The /T switch allows it to function recursively. Replace Administrator with the user you wish to give permissions to.
Source:http://superuser.com/questions/116625/recursively-change-owner-windows-7
