Follow this guide from start to end and do not leave a single step. 

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 : you will see 2 Dell data volt devices, please uninstall the second one (bottom one) . 

Reboot 

install SupportAssist