Are you actually placing these dlls in a folder named C:\items and registering them there?

Say it isn't so. This is definitely not the way to do it and can introduce problems in existing software as well. DLLS especially system DLLS belong in the system area and you must check to make sure that there is not already a newer version of this dll registered on the system.

Windows Vista and Windows 7 are likely preventing you from doing this as windows XP and the software police should as well.