Deleting duplicate dll:s

[Father Dagon]

Last summer I ran the trial version of Duplicate File Detective (www.duplicate-file-detective.com). What astounded me was the gigs and gigs of duplicate dll:s. I asked an acquaintance who is working as a programmer on how to not delete anyting important, but not even he had the slightest clue.

Does anyone know how to delete the unimportant dll:s? Please help!

[jsiv]

Are we talking about files with just the same name, or files that are actually byte-for-byte the same? Because if it's the first, then they may very well be different versions of the same library (DLL).

It's very common for programs to keep a local copy of libraries they need in their program folder to make sure they have exactly the right version and to prevent other programs from messing with it. Of course, this really only works if there's only one program that uses the library running, since a library is only loaded into memory once and then just has its reference count increased if a new program tries to load it. XP and up try to fix this by support running several instances of the same library alongside each other. This goes against the whole concept of shared libraries, but what can you do, the whole problem is caused by design decisions made long ago in a very different computer world.

Anyway, if the files are identical there is no reason why you shouldn't be able to delete all but one copy (kept in the common Windows folder) and still have the programs work. You can easily try it with no risk as long as you back the files up. Really though, the wasted space is probably insignificant these days.

[Father Dagon]

I'm not sure if they are byte-for-byte duplicates. I used an older version of DFD and the 128-bit algorithm considered them to be duplicates.

Later this month, when I get the dough, I will buy the latest version of DFD that uses byte-for-byte comparisions.

And the space might be insignificant if we are going to use linear mathematics. But I prefer control and perfection.

[Yalius]

Some of them may also be in folders with names like "$NtUninstallKB4896424$"; if so, those are backed-up older versions that windows update replaced. I typically wouldn't recommend deleting much of anything in the \windows or \windows\system32 folders, especially if things seem to be running OK.