What exactly are the "personal" files that are kept in the Windows 8 Refresh?

Question

I am going to help a friend clean his Windows 8 PC which is running slowly.

After some research I found that there are two options:

• Windows 8 Refresh
• Windows 8 Reset

Apparently, the Refresh option is less "destructive", and claims to keep the user's "personal files":

I would like to attempt this option first, and go for the Reset only if the Refresh doesn't solve the problem. Of course, all his personal files have been already backed up, but I am curious nevertheless:

What exactly counts as a "personal file"? In other words, what exactly are the files that will be kept in the Windows 8 Refresh? For example, will it keep files that are saved directly under C:\, such as C:\RandomSubfolder\foo.txt? Will it keep files saved directly on desktop? What if the HD is partitioned, and D:\ has a bunch of files (while windows is installed on C:\), will files on D:\ be kept too?

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Note: I found this very similar question on SuperUser but unfortunately the answers there don't precisely address my question. That question tells me that all desktop apps (and their data) will be removed, but doesn't answer the question of exaclty which files will be gone. On that question there is also a link to this page but unfortunately it doesn't seem to address my question as well, since it says:

Windows RE scans the hard drive for your data, settings, and apps, and puts them aside (on the same drive).

But does not give any extra detail about what "your data" actually is.

Answer 1

This reference gives you all the details you need to know:

https://technet.microsoft.com/en-us/library/jj126997.aspx

These folders are copied from the old Windows installation to the new Windows installation:

• \Users\profile: All files and folders except for \Users\profile\AppData.
• All folders at the root of the Windows partition added by the user. For example, C:\MyData.
• All file-history versioning data.
• All folders on non-operating system partitions.

The second and fourth bullet points answer your question nicely.

That said, if I were you I'd get a hold of an external hard drive and manually copy all documents, photos, videos, etc. as a backup, just in case. I've never lost personal files in a Windows 8/10 refresh, but it still pays to be safe than sorry.