How much data does de-NISTing remove from the C drive?

How much data can you expect de-NISTing to remove from the C drive of a Windows PC? Special Counsel provides e-discovery solutions to firms and helps them recruit attorneys. In 2018, they conducted a test of a PC running Windows 7 and found 38,489 files on the NIST list which totalled 6.9 GB. See the results posted here. Of this total, 6.725 files were Windows 7 system files.

A search of a Windows XP PC, found 25,744 files on the NIST list which came to 4 GB. Of these 4,049 were Windows XP files. This drive had recently been ghosted, with a new operating system installed and user files removed.

Special Counsel's review also targeted pagefile.sys system files which can be several gigabytes. As discussed in the Tip of the Night for May 16, 2016, this file stores memory for applications which have not been used recently.

Note that in Windows 10 you can review a breakdown of the types of files on the C drive in settings under System . . . Storage. It indicates how much data is taken up by Windows operating system files:

The official Reference Data Set (RDS) of the National Institute of Standards and Technology lists digital signatures for 28 million files, but does not include all system files.

When having hard drives processed, if you are being charged per GB for deNISTing, you should be sure to have the reviewer first sort through large files of 5 GBs or more in order to search for video or other files which are clearly irrelevant so your client is not billed unnecessarily.