Not sure, as I never use the product, but......
Since the upgrade to Windows 10, you've added a considerable number of gigabytes of files to your hard disk just between the installer download and the now "new" Windows.OLD folder, not to mention the extra bits of system files, assorted .dlls, .sys, .inf, .etc, .etc.
AND
IDK, how the application actually works, but you just rocked its' world and it woke up to living in a brand new house, so maybe it has to do some sort of superscan initially and subsequent scans, once things are sorted may return to a more normal time range.