Im upgrading my unlocked Pearl (originally purchased from T-Mobile but now using AT&T) to 4.2.1.164/4.2.1.101 and then plan to install the T-Mobile "LIST" theme ".cod" file into the java folder before installing the new OS.

Do I also need to change the blackberry.alx, file or any other file for that matter, to get everything working properly? If so, which .alx file do I need to replace?

Thanks!

If you want to load themes other than from T-Mobile, you'll need to replace BlackBerry.alx, otherwise you're all set.