Hello, I am using my friend's Mac and signed in as a "guest" When I was using her mac, the computer started to really slow down. Then finally gave me an error message saying something about "your start up disk has no space, quit applications or clear files" etc. I have saved few photos and documents on the desk top which I am still needing them. How do I clear up data ? I am not using any other application at the moment other than Safari. If I logged off as a guest, restart the computer, will I loose all the files ?