The easiest way to delete the temporary files is to go to
Start > Run > then type in box %temp%
and click on OK
this brings up all the temp files and then you click the cursor in a blank part of the right pane
then press Ctrl and A (at the same time) to select them all
then Delete to empty the folder.
I do this every so often.
Temp files are just that - Temporary, and can be deleted.