usasma

I would first check to see what programs are scheduled to perform scans around that time. Depending on the settings (daily, weekly, etc) it may take a while for it to recur.

When you open up Task Manager, go to the Processes tab.
Make sure that you click on the button in the lower left that says "Show processes from all users:
Then click on the View menu item, then on the Select columns menu item.
Place checkmarks in the I/O Reads and I/O Other boxes and click OK to exit the dialog.
Then expand the Task Manager window so that you can read the columns (you can double click on a column header to sort by that column).

Then wait for it to happen again - and check for the highest numbers in each of the columns. Let us know what you find and we can work from there.