Just noticed that I have no Opera directory in C:\Program Files. Instead, opera.exe, opera.dll etc are located directly in C:\Program Files. Is this normal, or (more likely) have I made a mistake at some time?

Sound strange. All my installations have kept their stuff in their program folders. I haven't kept up with updates though. The newest I have is 9.51.

Mine seems to be in /home/brian/.opera
- fwiw.

To quote your other recent post: "That doesn't seem to be a very helpful comment".

That sounds strange indeed. All my opera programs are in an Opera folder(s) under Program Files. All the settings and preferences are under Documents and settings in various folders. For example:
C:\Documents and Settings\Owner\Application Data\Opera\Opera800\profile\opera6.ini

Go to Help > About Opera and look there. All the paths to various parts are shown there.

Really? I thought Christian was asking whether it was "normal" for Opera to dump its files in some general "Program Files" directory, and since only a representative of Opera could give a normative answer, I assumed that anecdotal evidence would be welcomed. You'll notice that when Opera installed itself it made a directory called .opera in which it put the files. I hoped it might help to know that.

All those paths point to my User directory like they should.