200MB .mzz files in .NET 4.0 directory, what are they?

I am trying to make some space on a small C: drive and a search for large files has turned up two that I do not understand and cannot find a good description.

C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\SetupCache\Client\netfx_core.mzz
C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\SetupCache\Extended\netfx_extended.mzz

Does anyone know what these files are? There are over 200 MB in size for both of them. I would love to be able to recover that space, but I am afraid that they are needed.

Actually, I would hope that Windows is not using that much space for no reason.

Solution 1:

This page on Go 4 Answers implies that it's just a zip file:

6) Find the file netfx_Core.mzz and rename it with netfx_Core.zip and open with extractor

So if that's true and the fact they are in a folder called "SetupCache" implies that these are just the data files for the .net 4.0 installation.

If the installation is done and working then you should be safe to delete them. I'd either move them to another (larger) partition or back them up first just to be safe in case something still references them. In fact back up the entire contents of that folder before deleting.

Solution 2:

These are indeed just data files for the client and extended .net frameworks - but just remember that you cannot remove or update the framework without these files being in place, so if you do move them bear in mind you may need to move them back when the framework gets updates.