Replacing protected library files in use is a chore.  Yesterday, I had to replace some PGP 8.0 DLLs with debug versions so I could step through PGP code.  Since they are in use, I tried to use a Microsoft command-line tool inuse.exe to schedule those DLLs to be replaced after reboot.  Unfortunately, the files were protected by WFP (Windows File Protection).  So I disabled WFP temporarily by changing a registry setting.  Still a no go.  Frustrated, I tried something that shouldn't have worked.  I renamed the DLLs and copied over the replacement DLLs.  Now I am stepping through PGP to chase down a bug.  Windows security is unreal.