How do I make WMP default application for music CDs?

Hi, an easier step for WMP is to go to Control Panel, Programs and Features, Turn Windows Features on or off, find Windows Media Player and 'uninstall' WMP using that, then 'reinstall' it using that. I did that when I went looking for WMP's shortcut.

Oddly, and others have noted this, there are 2 folders containing WMP, one in Program Files, one in Program Files (x86) - and that's a clean Win 10 install. The contents are slightly different.
@Florio: don't expect all items from your Win 7 start menu to appear in the Win 10 start menu. They simply don't. The answer is to use Classic Shell - you can still use the Win 10 menu with a keyboard shortcut, but Classic Shell will feel a lot more comfortable- and you can launch universal apps from it too.

Win 10's start menu only seems to respect the top folders in a start menu structure and loses the rest now - it used to take (some of the) contents of the subfolders and show them in alpha order.

Great.. glad it worked. Note: for future reference:

an in-place upgrade install is one of the better things about Win 10:
This will refresh Windows, after the manner of a Windows installation.
- all/most associations will be unchanged
- all your programs will be left installed
- you will lose any custom fonts
- you will lose any customised system icons
- you may need to re-establish your Wi-Fi connection
- you will need to redo Windows updates subsequent to the build you have used for the repair install
- system restore will be turned off- you should turn it on again and I recommend you manually schedule a daily restore point.

And as each major build comes out, that's your updated reference build, and as updates are mostly cumulative, there will be few to do.