I have been wrestling with this for a bit.  I cannot get SupportAssist to install.  I tracked down the issue by finding the logs and also the windows events.  Found this:

Product: Dell SupportAssist -- Error 1714. The older version of Dell SupportAssist cannot be removed.  Contact your technical support group.  System Error 1612.

Search on forum didn't turn up much.  Google search turned up 2 year old posts with same problem but broken lings to places to download file.  

My programs still has an entry for Dell SupportAssistAgent which will not uninstall due to a missing SupportAssistAgent.msi file.  Search for files on all drives cannot find this file anywhere on my PC.

How do I go about uninstalling or removing any older installs so I can install SupportAssist properly,