Thanks. However I had already completely disabled updating. All of these:
Tools:Preferences:Advanced:Security:autoupdate = Do not check for updates
Kill it with fire:
C:\Util\NET\OPERA\updatechecker\opera_autoupdate.exe rename to x_opera_autoupdate.exe
about:config search for 'update'
Autoupdate Geo Server = https://autoupdate.geo.opera.com/ Clear it.
Autoupdate Server = https://autoupdate.opera.com/ Clear it.
Disable Opera Package AutoUpdate tick it.
But too late, it already had the update file and really, really wanted to apply it.
Anyway, I found the culprit just now, by looking through the Registry. This:
Ah ha! Here it is: C:\Documents and Settings\Administrator\Local Settings\Temp\CUtilNETOPERA
Goodness me, there's a virtually entire copy of Opera in there. I suppose it's used to have a running browser while patching the real copy.
Key update files being:
autoupdate.txt Urgh! This file is unicode-16, with 0x0A linebreaks.
Opera-12.16-1860.i386.autoupdate.exe size 12,848 KB the actual update file
I just renamed the whole folder CUtilNETOPERA to something else. Problem solved, browser works fine, no more popup nagging.
Opera didn't try to create a new copy, I guess since it's been told not to try asking for updates.
If I want to do the update for some reason I could rename it back.
Though in general I'd download the full new version 12.16, archive it, and install it.