Recording active webchat content.

I been thinking of using AviScreen Portable (http//www.softpedia.com/progDownload/Windows-Portable-Applications-AviScreen-Portable-Download-81008.html) which records the computer screen activities into .avi format, for evidence. The program runs from a usb drive and saves the captured video to the same usb drive. For example during a response to a house, I find content being displayed from a webcam, or other activity, that is not being saved to the hardrive, and once the system is shutdown, would require digging to find. The evidence we would be collecting does not need to be forensic clean, because it's not a new criminal charge, more of a violation of parole conditions, ie no federal trial out it. Still, I would prefer to be as close to forensic clean as possible, and just in case additional evidence is found at a later time. I would like to know if the program would create changes to the computer hardrives, or is it just registry keys and RAM being affected.