Sometimes, when software won’t install, especially something like ShadowProtect SPX which includes a driver, it is because of corruption of one or more internal Windows certificates. A method recommended to some extent in a few Microsoft resources:

certutil.exe -generateSSTFromWU roots.sst
Import-Certificate -FilePath .\roots.sst -CertStoreLocation 'Cert:\LocalMachine\Root' -Verbose

This does not always work. The only thorough method currently known to this writer, is to download this:

http://media.kaspersky.com/utilities/CorporateUtilities/rootsupd.zip

which contains a binary called “rootsupd.exe”. It will unpack itself if one runs it in administrative CMD, with syntax like this:

rootsupd.exe /c /t:C:\rootsupd

It will create the folder C:\rootsupd. Then go into C:\rootsupd, and do these (administrative CMD, not Powershell for some reason!):

updroots.exe authroots.sst
updroots.exe -d delroots.sst
updroots.exe roots.sst
updroots.exe updroots.sst

rootsupd.exe was, according to Google, available by download from Microsoft, but is not at this writing.

One does not have to reboot the system after doing the above, so far it just works.