You have already seen people fully desperate because their Windows system cannot boot.Of course, they could bring their PC back to the shop and ask for a complete re-install, but they will loose their data.There is a way avoiding that.Of course they will still have to go back to the shop and have the thing repaired.But they can, before that, save their files.There are Windows LiveCD distros, you can boot on a CD which has an embedded Windows.Because you boot off the CD-rom, the hard disk is not embedded. And as you boot off a CD, there is no virus problem, at least on the CD.So, you have a working windows environment, you see all the files on the hard drive, and you can give the mouse back to your friend, and he will drag-and-drop his files off his hard drive and push them on your USB flashdrive if the files are small, your USB external disk for more date.Nice, isn't it ?