Joomla! announced that the 1.0 -> 1.5 legacy plugin will no longer be included in the coming Joomla! 1.6.  - installation of older (1.0x) components, modules, etc. will no longer be possible. 

This is a good time to start migrating your site to 1.5.

Some of you may have noticed that our site is now running on Joomla 1.5.  We recently migrated because the latest version is a huge improvement in terms of ease-of-use, functionality, security and accessibility.   I have to admit that the migration process wasn't easy, but it was well worth it.  I like to share the step I have gone through and hopefully it would be helpful to you.