one way issues can begin is if you install an earlier version after a later one...

it's not really a warning, just a request - do you want to do this, for this version [and therefore change the default]

because you cannot [easily] change the default version for opening WEB/XAR files using windows, sometimes you need to edit the registry to make this request appear, so you can change the associations and therefore the version that opens them by default - for example, once you have said no to both and unticked the box that is the only way you can get the box to reappear for that version should you wish to change to yes