Remko Weijnen's Blog (Remko's Blog)

About Virtualization, VDI, SBC, Application Compatibility and anything else I feel like

Archive for January, 2018

signtool sign returns error 0x800700C1

I was trying to sign an .appx package that I created with the Desktop App Converter. However signtool returned the following error: Sign returned error: 0x800700C1
For more information, please see


Sadly signtool doesn’t return more detailed information, even when passing the debug switch:


So what’s going on?


  • Filed under: UWP
  • Case of the Crashing Task Scheduler

    Recently I installed a new Windows 10 machine (version 1709 aka Fall Creators Update).

    After a while I noticed a problem with the Task Scheduler: when I wanted to open the “Schedule Tasks” option from settings I received the following error message:

    The remote computer was not found.

    The Task Scheduler MMC snapin was empty:

    Task Scheduler (Local) | Empty


    DAC IconWhen using the Desktop App Converter there’s no need to sign the resulting .appx packages with your own code signing certificate when you submit them to the Store.

    However if you want to test the package on a different machine or distribute it to test users you may want to sign the .appx with a certificate.

    One option is to use the -sign parameter, in this case the Desktop App Converter generates a code signing certificate and signs the package with it. Although easy to use, it’s not very convenient if you want to distribute the .appx as you need to add the certificate to the Trusted People certificates store (for each user). See Run the Packaged App in the documentation.

    imageIf you want to sign the .appx package with a trusted certificate (e.g. issued by a trusted certificate authority such as DigiCert) you need to make sure that you pass the subject (the CN) from your code signing certificate to the Desktop App Converter (using the -Publisher parameter).


  • Filed under: UWP
  • How to remove Windows.old folder

    Just a very quick note here (mostly a note to self) but I had a couple of folder from previous Windows 10 installations named Windows.old Windows.old(1), Windows.old(2) etc.

    These folders should be removed when you use Disk Cleanup and select the “Remove previous Windows Installation(s)” option.


    However I already did that and for some reasons a subfolder named C:\Windows.old\Users\<username>\AppData\Local\Packages\Microsoft.Windows.Cortana_cw
    couldn’t be deleted and therefore the parent folder couldn’t be deleted.

    I couldn’t delete them with Windows Explorer nor via the cmd prompt or PowerShell. Then I tried to use the \\? prefix and that worked: