How to Overwrite System Files in Windows 7?
 

In Windows 7, changing system files would normally result to any of these errors:

Destination Folder Access Denied : You need permission to perform this action

File Access Denied: You need permission to perform this action

Then, you will be given the option to either try again or cancel. This happens because System files are protected by TrustedInstaller. Same thing happens even if the user is logged in as an Administrator. This does not give him the permission to overwrite the system files. If you want to prevent this from happening and you wish to overwrite system files when you need to, follow these steps.

1. Click on the Start menu. In the box provided, type "cmd", the right-click on the cmd.exe and select Run as administrator.
2. Next, you should take ownership of the file by typing the following: takeown /f C:\Windows\System32\wmpeffects.dll
3. Press Enter (substitute C:\Windows\System32\wmpeffects.dll with your file).
4. Then, you need to type in the following command: cacls C:\Windows\System32\wmpeffects.dll /G YourUsername:F
This will allow you to access the file. Press Enter.
5. Confirm you action by typing Y and press Enter one more time. Now you have the permission to successfully overwrite system files.