The Migration package is used if you are migrating from Altiris 6.0 to 7.0. If you're running a clean install of 7.0, then you don't need it.
Also 7.1 has been out for a while now and is overall a much better platform than 7.0. I would highly suggest upgrading/migrating to 7.1 (as it requires Server 2008 R2/x64, you'll need to move to another server). There is an abundance of KB articles, etc. with information on the migration process and planning, etc.