Missing DLL: aclui.DLL

Here’s a tip for you if you suddenly find a dll is missing. In my case, running WindowsXP, it was aclui.dll and this was preventing regedit.exe from running but it doesn’t matter which dll is missing, you should be able to find a copy on your computer:

First, look in the dllcache. There may be a copy there. You can find it here:
C:\WINDOWS\system32\dllcache

To see it you will need to have your folders set so you can see hidden files. To do that open the folder then from the Tools menu;

Tools > Folder Options > View (Tab) and scroll down and check the option to ‘View Hidden Files and Folders’

If you still can’t find the missing dll, then go to:
C:\WINDOWS\ServicePackFiles\

There should be a couple of folders there. Look in those. The missing dll should be there.

What to do with it once you have found it?

Copy the file then drop it into the System32 folder.
C:\WINDOWS\system32

You should be good to go!