is there any way some malicious software could go into that $folder in c:\ and with system privilages or rootkit in place, tamper or erase the files so that snapshots would be screwed ?
I've heard that is possible, but highly improbable. The reason for the unlikliness is due in part to the way FDISR's file structure. I think it goes something like this: The malicious software would have to be coded to work with FDISR's file stucture in order to be successful at doing what you pose and since it is unlikely that a malicious piece of software writer will target the relatively small number of users it is unlikely to be a threat. In other words, the amount of work it would take would not be worth the benefit of targeting such few users. I'm not an expert and I'm sure someone with more specific knowledge will have a more accurate and detailed answer to your question.
TECHWG, I have seen a lot of software. This is one of the best available that I have ever seen. I'm surprised that the company that owns the rights has not been acquired by either Symantec or Microsoft yet.
Every time good software comes around, some big stupid corporation buys it, waters it down and then stops supporting it!
I second third and quadruple that sentiment. I still haven't forgiven Roxio for selling Go-Back to Symantec.