Jesus. I did this once when I was troubleshooting the hostserver for a webapp. This server is running 2012, so for some reason you don't have the option to deselect "always use this program to open files of this type".
What happened was that I opened a .config file and selected notepad. I closed notepad by accident and reopened it without rethinking what I did. Suddenly all .config files where set to open in notepad and the webapp went down (luckily outside of prod time). I reset the extensions and went through the registry deleting all extension entries. But the damn .config files still had notepad as default.
After a long period of sweats and swear words and forehead smashing, I took a walk, did some googling and found this amazing application. It reset all extensions and worked like a charm. I slept well that night.
You can use Default Programs Editor to change the icon and description associated with a particular file type. When setting the icon's source, try browsing to the .exe that you like to use; they usually contain the appropriate icons.
Which version of Windows? Starting with 7, autorun.inf is ignored on non-optical drives since its main usage on USB disks was malware...
That's uh, really odd. Never seen Windows associate a different program when you JUST selected another. Not sure why that is but anyway, when all else fails you should be able to manually associate them with Default Programs Editor.
http://defaultprogramseditor.com/
It's free, and I use it to associate all ROM files rather than using built in auto-association. You can also use it to apply nice icons for files, if you'd like, so you can have a ROM look like that system's cart/disc. And it's actually a useful tool for all kinds of stuff. Never had an issue with it in the 5 years or so I've used it either.
You may not need instructions, but in case:
> third parties
Many big software companies collaborate with PA, and many others offer portable solutions themselves. The only annoyance is configuring default windows applications for each filetype (portable apps are not good at that since they avoid accessing the Registry), but Windows 10 will by itself change file associations anyway at its whim. Default Programs Editor was born to address this effectively.