I’ve had this annoying popup for ages. When you highlight an AVI file and hold SHIFT it often appears. This is most annoying when you want to move files (SHIFT+mouse) or force-delete (SHIFT-DEL).
I did some digging online and the best solutions I got were pointing me to a settings or configuration program within some XVid codec installs. Thing is, I don’t have those particular codecs so that didn’t help.
A bit of a dig later, courtesy of Process Explorer (formerly by sysinternals, now Microsoft) and I found that the program being used was one avisplitter.ax which can be found in C:/Windows/System32. I renames this (popped a “.bak” on the end)… and problem solved.
As far as I can tell, this has had no other effects on the system. Everything else seems to be working fine. However, I’ll leave the file in place rather than delete it just in case.