This is CNR's friend. The part that concerns me, upon having a second look at search results for lac97inf, is that the only place this filename seems to turn up is in temp folders of people complaining they have spyware problems. Some others, in asking for advice on spyware removal, have been told to remove that file in addition to a number of other things. The only strange thing about you is that your HijackThis log is almost spotless--there isn't even a reference to 'lac97inf' in the log, and no processes sticking out as abnormal.
My other thought is, if this is a legitimate driver or file, what is it doing in the temp folder? It should be in a system directory or program directory. Of course, DON'T put the file in any sort of system directory, since my suspicion is it doesn't belong there. While one website states this driver may be used by Windows, it never cites a specific application or process, there's no reference to it in any search I've done on Microsoft, and one other site lists the file as 'dangerous.' Though the program offered on that site itself seems fishy. I don't think it's causing troubles, but I do think it needs to be removed. What we need is a program that will free it from whatever other source is using it. And, at that, find out what is using it that makes it unremovable. It may also give us a clue as to what it's purpose is, and if dangerous, how to get rid of it.
I'd like to hear what an expert thinks about this.
