ActiveX DLL Registration (Page 6)

(6) In Which Directory should the ActiveX DLL be Located?

Put the DLL in any directory on a local hard drive. (Preferably the C: hard drive.)
Do NOT put the DLL on a remotely mounted or networked filesystem. Windows cannot trust the DLL and will treat it as something downloaded from the Internet.
After the DLL is registered, do not move it to another directory. The class named stored in the Windows registry points to the DLL path. If the DLL is moved or deleted, the registry will point to a file that does not exist.