I have always been a Nero fan, but I'm sad to say it's now virtually unusable (or more accurately, not upgradeable).
I believe that beginning with Nero 126.96.36.199 Installation package #2 (Showtime & Recode) that during the installation it slams/hijacks nearly 15-20 file application associations. Now if that's not bad enough, it does so in a way that makes Nero Showtime the "Restore to" default (an additional hurdle in XP).
While yes, I can attempt to restore my old association one by one, but should this really be necessary after every update or upgrade? Moreover, the solution is not so easy for some of us who have equipment like the DV500 which has intricate command-line functions tied to our AVI right-click options like "PinnaclePlay" with is entirely ERASED by merely upgrading Nero Install Package #2.
So, unless I missed some option in the Showtime Player or during installation, that ASKS if it's ok to slam the application associations, you might want to consider adding one. I remember when Realplayer used to resort to tacktics like this, but at least with them, there was a way to navigate to the right options during the install to prevent such a disaster. Is that asking so much?