Normally this is not something one has to worry about – unless of course one wants to use Google Chrome Portable or something like that.

Portable Chrome fails to set itself as default browser! It manages to configure itself to open HTML files, but it doesn't use the “portable” wrapper executable for this.

The “correct” way to change default browser is to use the Default Programs application, which is buried somewhere in the depths of the start menu. Of course this won't work for portable apps that the OS doesn't know about yet. As some badly written blog post informs me, the default URL handlers are stored in the registry at HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Associations\UrlAssociations; the ...\UserChoice\ProgId keys refer to programs defined in the HKEY_CURRENT_USER\Software\Classes hierarchy. If Chrome has already attempted (and failed, probably) to register itself, there will be a a corresponding class named ChromeHTML.* there.

Make sure the <Class>\shell\open\command\ key refers to (e.g.) ...\GoogleChromePortable.exe and not ...\App\Chrome-bin\chrome.exe!

When a suitable class is defined, it can be inserted into the ...\UrlAssociations hierarchy at the appropriate places.

It is also probably necessary to change some file associations (*.html and whatnot) but this is certainly easiest from the Windows shell.