Spark windows installs without error but will not launch

I am trying to install Spark - the install goes fine but everytime I try to launch Spark I get the following error:

“Windows cannot access the specified device, path or file. You may not have the a[ppropriate permissions to access the item”

This happens whether the user is a domain or local administrator or the application is run as an administrator. Spark version is 2.6.2 on Windows 7 Pro. There are no errors in the event log - I have searched on Google and on the forums and can’t find any mention of this problem.

Thanks in advance

oops, my antivirus - Sophos - is blocking the app.