I had a problem with my Surface Pro wanting to send crash info to Microsoft every time I started it. Someone suggested I run Disk Cleanup so this morning I did. I let it keep the downloaded website files, but cleaned everything else. There was over a gigabyte of junk that has accumulated already!! That fixed the problem. So I decided to try it on this desktop machine and while still keeping the downloaded website files, it found over 2 gb of junk to remove I was leery of using the option to cleanup SYSTEM FILES, so I skipped that. It's < probably > safe but I'm not sure about it. Might improve boot time if I cleaned those too, dunno.