Here is a small portable app that can record your desktop and save video in a few formats, it's portable so needs no installation, just run from flash drive/ext hdd and when finished simply delete.

Code:
https://www.softpedia.com/get/PORTABLE-SOFTWARE/Multimedia/Video/Easy-Screencast-Recorder-Portable.shtml
Supports WinXP, Vista, 7 ,8 and 8.1