Yes. They can, and should be, deleted periodically. You can
safely delete anything except those in use, but since Windows
won't let you delete a file in use, it's safe to try to delete
them all.
Just don't delete them automatically as soon as you boot. That
can screw up program installations that work in two steps--the
first step ending by saving temp files and rebooting; the second
step needing to find those temp files when the boot completes.
