Dell Support Assist Installation always failed

follow this guide from start to end

You may find that a few thing I am recommending to delete are already deleted from your computer so skip those steps.  

1 Use Microsoft's Installer : 

This step is crucial as Microsoft's uninstaller disables the services as well. Choose SupportAssist and uninstall, Uninstall Dell updates by running the the uninstaller again. If Support Assist doesn't show in List ignore this step. 

Reboot (important) 

2. Delete following folders and ignore the once which are already deleted. 

C:/ Program Data/ PCDR 

C:/ Program Data/Supportassist 

C:/ Program Data/Dell/Dell data volt 

C:/ Program Files/ Dell/Supportassist 

C:/ Program Files/ Dell/ Dell data Volt 

C:/ windows/Temp (everything inside the folder 

Remove these Registries 

Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services key.

Delete Dell hardware service, Delete Dell client management service, Delete Dell updates. 

Open device manager > system devices : If you see 2 Dell dala volt devices, please uninstall the second one. 

last step : Download dot net 

https://dotnet.microsoft.com/en-us/download/dotnet/thank-you/runtime-5.0.17-windows-x64-installer

if it's already installed, installer will give you option to repair or remove, choose remove and reboot. 

Install again. 

Reboot 

install SupportAssist 

I did all your advice but sad to say all doesn't work and say Installation failed. Please reboot your PC and try again, any other solution, please advise...