There are some built-in tools so that you can monitor what may be thrashing your disk. It should not be thrashing continuously once the system has settled.
As BBB says, Indexing may be party of the problem. After a fresh install of Windows, apps and data, it may take several hours for the index to finish building. If you rely on search, it may be worth waiting for it to finish. Definitely kill Defrag: it's a waste of time, resources and causes unnecessary hardware wear.
Anyway, open up the Resource Monitor and plot the disk activity to see if you can work out what is the main offender. It may just be a combination of initial indexing and initial AV scan that will stop after running to completion.
Regards: Terry
