A recent attempt to install CHX3 on an XPPro machine, resulted in repeated failures. The CHX drivers would not start. After much trial and error, the source was revealed to be avast! anti-virus. Uninstalling avast! resulted in a quick and clean install of CHX3. I have never encountered this problem before, and have used avast! for many years. CHX3 and avast! are happily running together on another machine, but both were installed over a year ago. I don't know what change in avast! has caused this to occur, but I didn't bother to try reinstalling avast!, just switched AVs. FYI.