I would say C:\WINDOWS\system32
There are already a lot of .dll files located there.

Never heard of extracting to a dllcache, don't even know if it's possible.

Thanks Randy, I just wanted to be sure.
I've never had a reason to try.

Now if you've downloaded a program in a zip file and it has a .dll that needs to be extracted, it would be extracted to
C:\Program Files\whatever program.

I am still having problems with this whole business of extracting .dll files.
Exact location.
and
Will they start to function.
I know they can be put at any location with the Wizard.
I will probably let this go for now until I get further information.

I found what I needed at this location.
dll-files

Huh?

I must have installed 50 mods that are .dll files. I might be missing something here, but they all come in various compressed formats and the appropriate unzipper is needed (which are free) to extract them to either my choice of a created folder for manual installation or a direct extract to their designated folder (in my case the game's data file folder containing meshes and textures etc.) I usually go for a manual drag n'drop installation because extracting them into their designated folder sometimes just doesn't happen.

What exactly are you trying to install (that might be some help)?

Reply to Martha.
I hope I found what I needed. Shown on my last post.

Thanks anyway. I just tamper with one part of my computer
or another just to learn and have something to do. It's a wonder it keeps working.
I guess I would try this first if I ever have a need.

1. Press Start and select Run
2. Type CMD and press Enter
3. Type regsvr32 "filename".dll and press Enter

If this doesn't work than I will try a specific location.`

The compressed download file should have a target that you can xtract directly to. Well, good luck.