Windows 7: unable to save permission changes on ExplorerFrame.dll

hey everyone,
Im trying to replace my explorerframe.dll to one that suits my visual style. Im using a program called windows theme installer, which does it for you. However it says that access is denied to changing files.
So i went into the system32 folder and gave myself full control on the explorerframe.dll file. I am now trying to give myself full control of the explorerframe.dll in the sysWOW64 directory too, but after pressing apply it says access is denied to saving changes.

I have windows 7 x64 service pack 1, and UAC disabled. A few weeks ago i did need to make use of the /sfc scannow command, as i rushed through some customization steps, could that be the cause or something similar?

Thanks for any help

I have literally changed hundreds of system files using this method below.
To properly change a system file you need to take ownership give yourself permission and rename the old file and then copy in the new one, look at Post #6 of this thread will tell you how to do it Basic Networking Information

Jerry

i got it working, thanks

You're Welcome