Use Windows Explorer, right click on the folder, check if there is a check by read only. If so, uncheck, then apply.
This is Windows "junk" folder. It should empty by itself unless you have a system crash, then stuff may get left behind. You can safely select all that's in this folder and delete it. Be sure to emtpy the recycle bin or you won't gain any space back. If Windows is doing something, you may not be able to delete all the files unless you shut down whatever application created the temp file. You can always leave those and it should clear once you shut down properly. Look for files with old dates, those for sure are no longer needed and are just junk you can safely ax.