Setup a hard drive or usb key with a re-installation image so that if they do experience trouble, they can just re-image their machine. All updates and software they need already installed.
Or you could have the system dual boot. Normal windows boot, but you can have them grub boot into linux and that will give you a pristine platform to log-in and save files/re-image their machine remotely via partition image. You have them boot into linux, and then you can operate on a comatose window partition without interference via ssh.