Can you see (view) that files into Windows Explorer? Can you delete them? Or booting in Safe Mode and trying to delete?

Are you showing hidden files and folders?
To unhide them, open any folder and go to Tools >folder options > View, then scroll down to where it says ‘Hidden files and folders’ and then check/tick the ‘Show hidden files and folders’.
Then again try and go into the _restore folder and clear the temp folder.

Tutorial here: http://www.bleepingcomputer.com/tutorials/tutorial62.html

Sometimes, only using Unlocker (http://ccollomb.free.fr/unlocker/) or Delete FXP (http://www.jrtwine.com/) you can delete files like that.