First turn off UAC
User Account Control - UAC - Change Notification Settings Option 1 (take note of your current setting before turning it off) after you are done changing your .dll/file turn the UAC back to your current settings. Be sure to restart after turning it off and then again when turning it back on.
Right click on the .dll/file and go to 'properties'.

Click on the 'security' tab. Click 'Advanced'.
Click on the 'Owner' tab. Click 'Edit'.
Select
your user and click Apply then OK.
You will get this if you have UAC on click OK.
Click OK on the next box.
Click OK on the next box.
Then OK on the final box.
Now right click on the .dll/file again and go to 'Properties'

Click on the 'security' tab. Click 'Edit'.
Select 'Users'. In the bottom part of the box, tick the box to allow 'Full Control' and click Apply then OK.
You will get this if you have UAC on click Yes.
Click OK then OK again on the last box.

You now own that .dll/file and have full permissions over it.
Now right click the .dll/file
Rename
Rename the .dll/file to .bak like shell32.bak.dll
Note: I use .old on shell32 all others I use .bak
Then paste in your replacement file.
You will have both .dll & .bak.dll if you need to go back.
Jerry