If you are trying to tweak or modify your Vista system, you will run into a barrier when it comes to replacing or changing system files. You can take ownership of the file and then grant your username full control of the file. After you have made your changes and/or modifications, you can then remove the permissions.
First you will need to access an elevated command prompt, to do this:
1. Click the Start button.
2. Click All Programs.
3. Go into Accessories.
4. Right-click on Command Prompt.
5. Select Run as administrator.
6. When the UAC Prompt appears, click Continue.
Once you have your elevated command prompt, follow these steps:
For our example, I am going to use the Bubbles screensaver file (Bubbles.scr)
1. At the command prompt, input takeown /f filepath (takeown /f c:\windows\system32\Bubbles.scr).
2. Press Enter on the keyboard.
3. A message will be displayed that this completed successfully.
4. Now input icacls filepath /grant yourusername:f (icacls c:\windows\system32\Bubbles.scr /grant gcham01:f).
5. A message will be displayed that this completed successfully.
You will now be able to modify or replace the file. When you are done, simply remove the permissions to keep the file secure.