Hold down the Shift key before clicking on that file. This will mark all the files in that date range, in all folders. Now right-click on any of them, and from the context menu, select Delete. They should all disappear in one fell swoop. Use the Defrag command now to clear fragmentation.
Fragmentation is a normal process when a computer writes data to a hard disk.
As new information is updated, it is written to the hard disk. Many times it cannot find a space large enough to record the information in a single string. When the data is read, the read head has to jump to various locations on disk. This slows down data retrieval. This is where Defrag comes in.